Make location of sidebar/panel configurable

Introduce an instance setting to allow configuration of the side panel. Suggested boolean setting name is rightHandSideBar.

It is hardcoded in our PleromaFE branch with this change:

--- a/src/App.scss
+++ b/src/App.scss
@@ -432,6 +432,7 @@ nav {
   flex: 1;
   flex-basis: 345px;
   width: 365px;
+  order: 99;
 }

feld/pleroma-fe@e46c88a7