Fix dead link in CONTRIBUTING.md (+ grammar fix) (#4921)

* Fix 404 link

* Grammar edits

CONTRIBUTING.md

@@ -42,7 +42,7 @@ Unsure of how to get started contributing to Red? Please take a look at the Issu
 * beginner - issues that can normally be fixed in just a few lines of code and maybe a test or two.
 * help-wanted - issues that are currently unassigned to anyone and may be a bit more involved/complex than issues tagged with beginner.
 
-**Working on your first Pull Request?** You can learn how from this *free* series [How to Contribute to an Open Source Project on GitHub](https://egghead.io/series/how-to-contribute-to-an-open-source-project-on-github)
+**Working on your first Pull Request?** You can learn how from this *free* series [How to Contribute to an Open Source Project on GitHub](https://app.egghead.io/playlists/how-to-contribute-to-an-open-source-project-on-github)
 
 At this point you're ready to start making changes. Feel free to ask for help; everyone was a beginner at some point!
 

README.md

@@ -131,4 +131,4 @@ Artwork created by [Sinlaire](https://sinlaire.deviantart.com/) on Deviant Art f
 Bot Project.
 
 This project vendors [discord.ext.menus](https://github.com/Rapptz/discord-ext-menus) package made by Danny Y. (Rapptz) which is distributed under MIT License.
-Copy of this license can be found in [discord-ext-menus.LICENSE](redbot/vendored/discord-ext-menus.LICENSE) file in [redbot/vendored](redbot/vendored) folder of this repository.
+A copy of this license can be found in the [discord-ext-menus.LICENSE](redbot/vendored/discord-ext-menus.LICENSE) file in the [redbot/vendored](redbot/vendored) folder of this repository.