fix: AM/PM will not be matched if it is part of the text

[teisermann]

Fixes: #312

[ivan-lednev]

Hello, @teisermann, thanks for taking the time to create this PR!

This seems like an overly complicated way to do something, that can be accomplished by updating this regex: https://github.com/ivan-lednev/obsidian-day-planner/blob/dfd17e7a29e85be5147d37aa2aec364ed2cbe390/src/regexp.ts#L16

to include something like this:

What do you think?

[teisermann]

Hello @ivan-lednev Thanks for the feedback, i think your suggestion is wonderful and i adjusted my pr accordingly I used a non negative lookahead instead of the not-word matcher to avoid accidentally matching the - for timestamps