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
Lily Ballard
207b5d81bf