Add support for yamllint config file

[revi]

yamllint looks for .yamllint file before looking for .yamllint.yaml or .yamllint.yml.

• [x] Added a change log entry in changelog.d/<directory>/.
• [x] Added self to copyright blurb of touched files.
• [x] Added self to AUTHORS.rst.
• [x] My changes do not contradict the current specification.
• [x] I agree to license my contribution under the licenses indicated in the changed files.

[!NOTE] This somewhat depends on #1123 in which merging 1123 will add AUTHORS.rst and copyright header correctly, so I checked them.

[floriansnow]

LGTM. Please ping me here once https://github.com/fsfe/reuse-tool/pull/1123 is merged in case I forget so we can merge this one as well.

[carmenbianca]

LGTM, merging, thanks @revi!