This updates the website to use the svg icons instead of the png ones (which BTW looks so much better because it is sharper).
It also updates several .gitignore files to exclude content that is generated by the website's build process and removes a file, that was accidentally commited and is generated by the build process.
@kaikreuzer I luckily found the code that generated the iconset page - would have been too bad if the broken iconset page would move into the stable website deployment with the 4.1 release.
As I reported in https://github.com/openhab/openhab-docs/issues/2169, the classic iconset page was not showing any icons due to https://github.com/openhab/openhab-webui/pull/2084.
This updates the website to use the svg icons instead of the png ones (which BTW looks so much better because it is sharper).
It also updates several .gitignore files to exclude content that is generated by the website's build process and removes a file, that was accidentally commited and is generated by the build process.