Match dependabot.yaml files in language server

[fionn]

The language server understands that Dependabot files match **/.github/dependabot.{yml,yaml}, however later on we check for dependabot.yml explicitly, thus excluding dependabot.yaml files.

We add dependabot.yaml as a file name to match against in the same manner as our matches for action.yml or action.yaml.

This has been tested in Neovim with the standard nvim-lspconfig settings, using

vim.lsp.config("zizmor", {
    cmd = {"/path/to/zizmor/target/debug/zizmor", "--lsp"}
})

to override the executable.

Closes: #2025

---

Pre-submission checks

Please check these boxes:

• Mandatory: This PR corresponds to an issue (if not, please create
  one first).

• Having read the AI policy, I hereby disclose the use of an LLM or other
  AI coding assistant in the creation of this PR. PRs will not be rejected
  for using AI tools, but will be rejected for undisclosed use or
  use that violates the policy.

If a checkbox is not applicable, you can leave it unchecked.

[woodruffw]

Thank you @fionn!