feat: document mise configuration to install bt

[Cedric / ViaDézo1er (viadezo1er)]

❯ ls -a
mise.toml
❯ cat mise.toml
[tools."github:braintrustdata/bt"]
version = "0.15.1"

# Optional, to specify the expected sha
[tools."github:braintrustdata/bt".platforms]
macos-arm64.checksum = "sha256:dca05a9d4b694c24e91e4d771d9d954fd6372079c8f72f2709f6e68478f0eb28"
macos-x64.checksum = "sha256:e81155f6d894ef44c653ced9a5b5fc9ba1a2ccc7765c41ada1e8baa345e09d2f"
linux-arm64.checksum = "sha256:1ff86377e1d6fcaccf9a6f6496a8e94eff7298f44cb98906c97518c9fa2bb73e"
linux-x64.checksum = "sha256:2fab9f8ece4ac2c66386206fa5f9d905e076da59d95e35423d641c24525740b1"
linux-x64-musl.checksum = "sha256:a33dea199b74c3282ef1aab5fab916cf9e22b5e11e396e6ef012a104c90fea1a"
windows-arm64.checksum = "sha256:2cc328337965997a23c95be20dd88318602aac76f5a35311675f416d46095771"
windows-x64.checksum = "sha256:70f7d7cfebfd978c3e475e13ac035e8931797ead33d1171073520470785f1244"
❯ mise install
github:braintrustdata/bt@0.15.1 extract bt-aarch64-apple-darwin.tar.gz                                                                        ✔
❯ type bt
bt is /Users/cedric@braintrustdata.com/.local/share/mise/installs/github-braintrustdata-bt/0.15.1/bt
❯ bt -V
bt 0.15.1

[github-actions]

Latest downloadable build artifacts for this PR commit 5f36875521cd:

• Workflow run: https://github.com/braintrustdata/bt/actions/runs/29130647603
• Download all artifacts (GitHub CLI): gh run download 29130647603 --repo braintrustdata/bt
• Installers are published from main automatically. To publish one for a PR branch, run release-canary manually via workflow_dispatch.

Available artifact names

• artifacts-build-global
• artifacts-build-local-x86_64-apple-darwin
• artifacts-build-local-aarch64-pc-windows-msvc
• artifacts-build-local-x86_64-pc-windows-msvc
• artifacts-build-local-x86_64-unknown-linux-musl
• artifacts-build-local-x86_64-unknown-linux-gnu
• artifacts-build-local-aarch64-apple-darwin
• artifacts-build-local-aarch64-unknown-linux-gnu
• artifacts-plan-dist-manifest
• cargo-dist-cache