Updated Contributing to Jellyfin (markdown)

Contributing-to-Jellyfin.md

@@ -56,6 +56,7 @@ If it's your first time contributing code, please add yourself to the `CONTRIBUT
 
 When submitting a new PR, please ensure you do the following things. If you haven't, please read [How to Write a Git Commit Message](https://chris.beams.io/posts/git-commit/) as it is a great resource for writing useful commit messages.
 
+* Before submitting a PR, squash "junk" commits together to keep the overall history clean. A single commit should cover a single significant change: avoid squashing all your changes together, especially for large PRs that touch many files, but also don't leave "fixed this", "whoops typo" commits in your branch history as this is needless clutter.
 * Write a good title that quickly describes what has been changed. For example, "Adds LDAP support to Jellyfin".
 * For anything but the most trivial changes that can be described fully in the title, write a PR body to describe, in as much detail as possible:
    1. *Why* the changes are being made. Reference specific issues with keywords (`fixes`, `closes`, `addresses`, etc.) if at all possible.