Add troubleshooting section for Apache

[kensanata]

Documentation improvement

Added a troubleshooting section to help others deal with the issues I had because I didn't start with a clean Apache setup so it was hard to figure out what to remove.

• I/we have read the GoToSocial contribution guidelines.

[igalic]

👍

my main issue has always been: streaming doesn't work, which means you need to reverse proxy ws, which needs mod_rewrite

[tsmethurst]

Thanks!