ref: 0.3.0 aerc/filters d---------
Strip carriage returns (^M) when filtering emails

Presumably some email servers will transform newlines into carriage
return new lines to better support windows users. I can't prove this but
that's the best explanation I have for my hosted email provider

Without this patch, I was seeing annoying `^M`s at the end of every
filtered line.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Escape plus symbol in hldiff filter.

I was getting errors when using the hldiff filter with aerc
because the plus symbol on line 28 wasn't escaped. This commit
escapes the plus symbol in the regex on line 28.
Move contrib -> filters