feat: regex manager (#5617)

docs/usage/configuration-options.md

lib/config/__snapshots__/validation.spec.ts.snap

lib/config/common.ts

lib/config/definitions.ts

lib/config/validation.spec.ts

lib/config/validation.ts

lib/manager/common.ts

lib/manager/index.ts

lib/manager/regex/__fixtures__/Dockerfile

lib/manager/regex/__snapshots__/index.spec.ts.snap

lib/manager/regex/index.spec.ts

lib/manager/regex/index.ts

lib/manager/regex/readme.md

...rkers/repository/extract/__snapshots__/index.spec.ts.snap

lib/workers/repository/extract/index.spec.ts

lib/workers/repository/extract/index.ts