feat: add XML format via prettier

[b0inbot]

Added XML as a supported formatter and make it use prettier by default. I am not interested in using prettier myself but it's already configured so I might as well.

Changes are visible to end-users: yes/no

• Searched for relevant documentation and updated as needed: yes
• Breaking change (forces users to change their own code or config): no
• Suggested release notes appear below: no

Test plan

• New test cases added
• Tested on my own repo with a custom xml formatter.
  • Commit is here but i do not expect you to run it yourself b0inbot/tools@0b13ed0
• unable to test via bazel run format within the example/ folder (Error running code complaining about libcrypt so.) Hoping CI/CD within ubuntu can run the test case.
• test folder does work:

$ pwd
/home/boin/Projects/tools/tools/rules_lint/format/test
$ bazel run format 2>&1 | grep -i xml
+ prettier --write example/checkstyle-suppressions.xml example/checkstyle.xml example/ktlint-baseline.xml example/pmd.xml example/spotbugs-exclude.xml example/src/hello.xml
Formatted XML in 0m0.011s

[CLAassistant]

All committers have signed the CLA.

[alexeagle]

Ah, I found this didn't actually function because the new plugin wasn't declared as a dependency. Will fix in a followup