fix: Support other DuckyScript commands in Syntax Highlighting - #3

Hi @webbrain-one ! Thanks again for the contribution. I've tested your implementation and made a few refinements on top of it. Could you please enable Allow edits from maintainers on this PR? I'd like to push the improvements directly to your branch so that your original PR and contribution remain fully credited.

Thanks again @webbrain-one — I've pushed my refinements directly onto your branch, on top of your commit, so your original work and authorship stay intact in the history and in the merge.

What I changed on top of it:

• passed the legend to registerDocumentSemanticTokensProvider and switched to the numeric SemanticTokensBuilder.push overload, so the branch compiles
• declared duckyscriptCustomCommand in contributes.semanticTokenTypes and mapped it to support.function.builtin.duckyscript, so custom commands get coloured in any theme
• enabled semanticHighlighting in the two bundled themes, which shipped with it off
• built the match from the configured command list (escaped, case-insensitive, longest-first) and fixed the start column on indented lines
• disposed the configuration listener and emitter, and honoured the cancellation token

The feature is yours — I'll merge with a merge commit so your authorship is preserved. Thanks for pushing this forward, and thanks to @i-am-shodan for the original request.