README.md: improve instructions to delete previous build cache
Sync upstream to https://github.com/Chatterino/chatterino2/commit/fda51f0d3a4a5cd15f099b951b796e299d566e9e
Sync upstream to https://github.com/Chatterino/chatterino2/commit/76b983a5b20dfa5fb116dcc6ada1849ca28ba471
Sync upstream to https://github.com/Chatterino/chatterino2/commit/f892a2df8b3fab0027d2cd1dfd357d8e23b3b140
Sync upstream to https://github.com/Chatterino/chatterino2/commit/f9d43313e8ad0a610c2b270241ab6112d1dfcbab
sync_to_upstream_fetch_patch.sh: add function to generate automatically also the Git-diff patch
betterlogger.patch: delete
README.md: add instructions to create patches for both GNU diff and Git diff