Add alternate extension-based support for ActionScript files

[admvx]

There was language-based support for ActionScript files already, via the nextgenas extension, but this adds a second version (disabled by default) for .as files, which aligns more with Adobe's branding.

Changes proposed:

• Add
• Delete
• Fix
• Prepare

[codecov]

Codecov Report

Merging #1765 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #1765   +/-   ##
======================================
  Coverage     100%    100%           
======================================
  Files          52      52           
  Lines        3003    3003           
  Branches      156     156           
======================================
  Hits         3003    3003

Impacted Files	Coverage Δ
src/icon-manifest/supportedExtensions.ts	100% <ø> (ø)	⬆️

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[JimiC]

You should add the languageid and remove the file extension. This way someone can still benefit from the syntax highlighting and the alternative icon.

[admvx]

Ah, sorry for missing that! I switched out the languageid as I personally don't use any specific VSCode extension with ActionScript, but I can remedy that separately.