Register bun.lock as JSON

[RiskyMH]

Description

Bun recently added a text lockfile called bun.lock (https://bun.sh/blog/bun-lock-text-lockfile) and it will soon become default.

It is also expected to only have one bun.lock file at root. At time of writing there was at least 200 repos (and still quickly growing), but it seems like github search count randomly fluctuates +/- around ~30 results.

Checklist:

• I am adding a new extension to a language.
  • The new extension is used in hundreds of repositories on GitHub.com
    • Search results for each extension:
      • https://github.com/search?type=code&q=NOT+is%3Afork+path%3A*bun.lock
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/oven-sh/bun/blob/main/packages/bun-vscode/example/bun.lock
    • Sample license(s): MIT
  • I have included a change to the heuristics to distinguish my language from others using the same extension.

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Although bun.lock officially uses JSONC, this PR sets it to standard JSON. Bun only relies on the trailing comma feature, which JSON happens to support without errors. The main reason to use standard JSON is that it provides better syntax highlighting on GitHub (#6197)