C journal stuff

This is just for learning, but it might be useful.

Adding some changelog

• we add a -x flag
• we can omit archive files from the search if we wish
• this makes it faster
• I wanted to do this because it makes things better

TODO

• Store the found files in an array, but use realloc().
• DONE Refactor the walking code into a function
• DONE Look for .txt files as well as Markdown files