Inconsistent parsing of non-org keywords between hl-todos and magit-todos

[elfsternberg]

I write technical documentation, and I mostly write in Markdown. While writing documentation, I frequently have to leave a placeholder for a future pass, which often reads like this: [TK: Where is this event handler defined?]. ("TK" is writerspeak for "to come" since the only words that have 'tk' in them are pocketknife and hotkey, and case sensitivity matters.)

If I use hl-todo in a buffer with TK notes, it works. It does not work with magit-todo. If I put a space in front of the letters, so it looks like [ TK: ...], then it works with magit-todos, but that's nonstandard and unaesthetic.

Expected behavior is that hl-todos and magit-todos find the same todo entries.

[alphapapa]

As noted on #125, I don't think I necessarily intended that magit-todos behave exactly the same as hl-todo in this regard; the use of hl-todo in this package is mostly for convenience regarding display faces. Anyway, see discussion there.