Register deno.lock as JSON

[spenserblack]

Description

Checklist:

• I am adding a new extension filename 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%2F%28%5E%7C%5C%2F%29deno%5C.lock%24%2F+version
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/denoland/wasmbuild/blob/a184c9249423aa5bc30e2d393a7ea74af9341fc4/deno.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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BTW, I wasn't sure if I should mark this as generated or not. While it is auto-generated, it looks like some lock files are deliberately not marked as generated (#4348).

[lildude]

LGTM. Thanks.

Note: this PR will not be merged until close to when the next release is made. See here for more details.