Add ability to parse XML clover files

[emibcn]

I have added:

• xml2json dependency in package.json. It forces to add dist/build/Release/node_expat.node to the repo
• TS models for the imported XML
• A translating function from the XML to the already used coverage-summary.json structure
• Some tests

I have changed:

• Default file to parse: coverage/clover.xml
• Github workflow to generate and parse self coverage test
• README, action.yml and package.json to reflect repo change and differences

Also, the process has added automatically the coverage badges to .github/badges/ using the results from nuning npm test -- --coverage ;)

It will probably be better to make a generic parser dispatcher and put there the 2 existing parsers and the new ones. Also add an option to let the user force the parser type. Now it's autodetected by file extension: if file name ends with .json, use original, if not, use clover XML parser.