Provide JSON files with extension information that work for specific or all TYPO3 versions

Examples:

fileadmin/ter/extensions.json => All extensions
fileadmin/ter/extensions.v9.json => All extensions working with TYPO3 v9
fileadmin/ter/extensions.v10.json => All extensions working with TYPO3 v10

Additionally add a json-file.md5 file for fast check if file has changed