This teaches `filterANSIEscapes()` how to find the end of an OSC sequence. It also keeps OSC 8 (hyperlinks) when not instructed to filter out all escapes, just as it keeps colors. This also relaxes the parsing of CSI escapes to find the end of the sequence for invalid sequences, and handles better escapes that don't start CSI or OSC. This fixes the repl output for `:doc builtins.fetchGit`. Fixes: https://git.lix.systems/lix-project/lix/issues/160 Change-Id: Id0000000f2a6956c042c883a4545edf347fa1799