more user‐friendly handling of chat commands

1. Come up with a proposal (all-inclusive?) and post it as an Issue on the CHQ repo: https://github.com/Charcoal-SE/SmokeDetector/issues
2. discuss which to include and exclude
3. create PR with the consensus

Items:

• report: make the split more forgiving (https://github.com/Charcoal-SE/SmokeDetector/pull/10755): change urls = argsraw[0].split(' ') to urls = argsraw[0].split(sep=None)
• reject: !!/reject 12345 5 false positives, no known hits.: account for \d+ (19+ characters)
• reject: maybe make exceptions for < 19 chars if: 'superseded by \d+' or match('author') && match('request')
• watch: allow leading whitespace
• addblu: allow a trailing comment (and throw away the comment?)