Deprecate Hook t3lib/class.t3lib_parsehtml_proc.php:transformation in RteHtmlParser
Since the deprecation of several internal functions in the RteHtmlParser in TYPO3 10.2 (https://docs.typo3.org/c/typo3/cms-core/10.2/en-us/Changelog/9.5/Deprecation-86440-InternalMethodsAndPropertiesWithinRteHtmlParser.html) the hook t3lib/class.t3lib_parsehtml_proc.php:transformation became quite useless.
It is now impossible to access the tsconfig configuration and other information that you would need for examples that we had the documentation like here: https://docs.typo3.org/m/typo3/reference-coreapi/master/en-us/ApiOverview/Rte/Transformations/CustomApi.html
The hook is not being used in the core.
It has been used in some extensions in the past: https://github.com/search?q=t3lib_parsehtml_proc+filename%3Aext_localconf.php+language%3APHP+language%3APHP&type=Code&ref=advsearch&l=PHP&l=PHP
However these extensions don't seem to be maintained anymore