Add TextMate Grammar for Verilog/SystemVerilog Highlighting

[clysto]

This PR adds a TextMate grammar to the Verible VS Code extension to provide proper syntax highlighting for SystemVerilog files.
The grammar is adapted from vscode-verilog-hdl-support, with minimal adjustments to integrate cleanly into the existing extension structure.

Before this change, the extension lacked built-in syntax highlighting and relied solely on LSP diagnostics. With the added grammar, users now get immediate and consistent token coloring without installing an additional extension.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: clysto / name: Yachen Mao (f6da265)

[clysto]

Any suggestions?

[hzeller]

I like the idea, but I am wondering how it interferes is someone already has a system verilog plugin installed ? If so, their coloring should precedence as the Verible plugin would only do that as secondary functionality.
Do you know how these things are configured ?

[clysto]

Multiple extensions can contribute grammars. If several installed extensions provide a TextMate grammar for the same language (e.g., SystemVerilog), VS Code will pick one based on the language id and the extension’s contributions. There isn’t a user-visible “precedence” setting exposed in the UI—you normally see one set of highlight rules applied. Extensions can override or replace existing grammars by contributing a grammar under the same language id. 

If someone already has a SystemVerilog plugin with its own grammar installed, VS Code will pick one grammar to apply. There isn’t a native per-extension “precedence” setting for TextMate grammars; the editor resolves this based on the active language id/grammar contributions. If desired, users can override the grammar selection manually in the editor for their workspace.

[hzeller]

mmh, this does sound it can result in surprising effects for users (in particular existing users of the Verible plug-in that I expect typically already have another plug-in installed for the syntax-highlighting).

Could there be a configuration option that we can offer in the Verible plug-in to use or not use the grammar ? The VSCode options pane allows for configuration options that are provided in the package.json and I wonder if we can have a 'checkbox' configured in the plugin json to then toggle if the grammar is active ? (we can have it default on, but at least it would allow people to switch off things)

[RedCMD]

VSCode provides no way to configure TextMate grammars
the only options are to disable/enable the extension
and staticly via the alphabetical ordering of extension names publisher.name
Z is higher than A

you could add a different language id
to separate them
but then you'll have separate languages

users of the Verible plug-in that I expect typically already have another plug-in installed for the syntax-highlighting

are the grammars not the same?