Add Vitepress docs (#326)

* Add vitepress for docs

* some fix

* Use vitepress and update docs

* Use vitepress and update docs

* Update README.md

* Add favicon

* Add docs by @jiriks74

Co-authored-by: jiriks74 <jiri@stefka.eu>

---------

Co-authored-by: jiriks74 <jiri@stefka.eu>

docs/update.md

@@ -1,4 +1,4 @@
-# Update
+# Update Opengist
 
 ## Make a backup
 
@@ -40,6 +40,7 @@ chmod +x opengist
 Stop the running instance; then pull the last changes from the master branch, and build the new version.
 
 ```shell
+git switch master
 git pull
 make
 ./opengist