[CI] Textlint: convert rc file to YAML so we can add comments etc

[chalin]

Some of the patterns in the textlintrc file would warrant some explanation. It's easier to use YAML in such a case, since it supports comments. Textlint supports YAML, among other formats for its config file.

I'll wait for the currently pending PRs over textlint config to be merged before making this change -- waiting on the merge of:

• [CI] Textlint: properly check for Java capitalization & more #3497
• [CI] Terminology fixes from patched terminology textlint rule #3496
• [CI] Textlint repo .md files, and new link-checker #3491

[svrnm]

great stuff, merged :-)