Fix installation link

Author: unixfox

README.md

@@ -3,7 +3,7 @@
 Companion for Invidious which handle all the video stream retrieval from YouTube servers.
 
 ## Documentation
-- Installation guide: https://docs.invidious.io/companion-installation/
+- Installation guide: https://docs.invidious.io/installation/
 - Extra documentation for Invidious companion: https://github.com/iv-org/invidious-companion/wiki
 
 ### Local development