Add chat shortcuts script

[Exagone313]

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[Exagone313]

notes for review:

• I can change or remove the license header
• the list of weapons was done using a mix of pickup names, partial means of death and a little guessing, this could be improved
• etpub has [l] (player location name, computed by BG_GetLocationString) and [p] (last player looked at), but these two would require an implementation in legacy, so I omitted those