Add rule template and documentation (#2215)

* Add rule template and documentation

* Correct H-levels for Parameters

* Remove duplicated examples

Author: sdwheeler

docs/rule-template-docs.md

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+# PSScriptAnalyzer rule template guidance
+
+The [rule-template.md](rule-template.md) file illustrates the structure of the PSScriptAnalyzer rule
+articles. Replace all placeholder text, then remove optional sections that don't apply.
+
+## Required content
+
+Every rule article starts with these YAML frontmatter fields:
+
+- `description`
+- `ms.date`
+- `ms.topic: reference`
+- `title`
+
+Place the H1, severity line, and default-state line immediately after the frontmatter. Follow them
+with `## Description`, which explains the diagnostic, why it matters, and the preferred alternative.
+
+Each rule must have an `## Example` section. Each example includes a `### Noncompliant` code block
+followed by a `### Compliant` alternative. Give each scenario an H3 heading and use H4 headings for
+its noncompliant and compliant code pair.
+
+Every rule article includes `## Configure rule` after its example or examples. For a configurable
+rule, include a `Rules` hashtable entry. For an always-enabled or otherwise nonconfigurable rule,
+use the following text.
+
+```markdown
+This rule is always enabled and isn't configurable. Use one of the following methods to avoid using
+this rule:
+
+- Create a custom rule configuration file to include only the rules you want or exclude the rules
+  you don't want.
+- Add the appropriate rule suppression attributes to your code to suppress the rule for specific
+  code blocks. For more information, see the _Suppressing rules_ section of
+  [Using PSScriptAnalyzer][02].
+```
+
+## Optional sections
+
+Use an additional H2 explanatory section between `## Description` and the example when readers need
+context before reviewing the code. Existing articles use this space for compatibility profile
+information, reference tables, supported values, and remediation guidance. For examples, see the
+following articles.
+
+- [AvoidUsingConvertToSecureStringWithPlainText](Rules/AvoidUsingConvertToSecureStringWithPlainText.md)
+- [UseConsistentParameterSetName](Rules/UseConsistentParameterSetName.md)
+- [UseConstrainedLanguageMode](Rules/UseConstrainedLanguageMode.md)
+
+When the rule is configurable, include `## Parameters` section after `## Configure rule`. Use an H3
+heading for each setting and document what it controls, accepted values, and its default value.
+
+After the `## Configure rule` and any parameter sections, include a `## Suppression` section only
+when the rule needs specific suppression syntax or examples. Otherwise, link readers to the general
+_Suppressing rules_ guidance from **Configure rule**.
+
+In the `## Further reading` section, provide links to additional resources that help readers
+understand the rule, its context, or related topics.
+
+## Final checks
+
+- Include `## Configure rule` for every rule article.
+- Include `### Parameters` only for configurable settings that need individual documentation.
+- Pair noncompliant code with a practical compliant alternative.
+- Remove all unused optional headings, placeholder text, and link definitions.

docs/rule-template.md

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+---
+description: {{Brief description of the rule behavior}}
+ms.date: {{MM/DD/YYYY}}
+ms.topic: reference
+title: {{RuleName}}
+---
+# {{RuleName}}
+
+**Severity Level: {{Error | Warning | Information}}**
+
+**Default state: {{Enabled | Disabled | Always enabled}}**
+
+## Description
+
+{{Explain what the rule detects, why the pattern is a problem, and the recommended
+practice.}}
+
+## {{Optional explanatory topic}}
+
+{{Add a table, supported values, compatibility information, or remediation guidance
+when the rule needs context before its examples. Remove this section when it doesn't
+apply.}}
+
+## Examples
+
+### Noncompliant
+
+{{Describe the scenario as necessary.}}
+
+```powershell
+{{Code that produces the diagnostic}}
+```
+
+### Compliant
+
+{{Describe the scenario as necessary.}}
+
+```powershell
+{{Equivalent code that doesn't produce the diagnostic}}
+```
+
+## Configure rule
+
+{{For a configurable rule, use the following configuration and include the Parameters
+section. For a nonconfigurable rule, replace this text with an explanation that the
+rule isn't configurable and describe available exclusion or suppression options.}}
+
+```powershell
+@{
+    Rules = @{
+        PS{{RuleName}} = @{
+            Enable = $true
+            {SettingName} = {Value}
+        }
+    }
+}
+```
+
+## Parameters
+
+### {{SettingName}}
+
+{{Explain what the setting controls, its accepted value type or values, and its
+default value. Add another H3 section for each setting. Remove this section for a
+nonconfigurable rule.}}
+
+## Suppression
+
+{{Explain any rule-specific suppression syntax or examples. Remove this section when
+general suppression guidance linked from Configure rule is enough.}}
+
+```powershell
+[System.Diagnostics.CodeAnalysis.SuppressMessageAttribute('PS{{RuleName}}', '')]
+```
+
+## Further reading
+
+- {{[Article title][01]}}
+- [Using PSScriptAnalyzer][02]
+
+<!-- Link references -->
+[01]: {{URL or absolute path}}
+[02]: ../using-scriptanalyzer.md