Fix loading of plugins (#6750)

* Explicit load plugins for the settings editor

* Move logic to the tree extension

* Move logic to a separate plugin

* Read extensions in webpack config

* Rearrange package.json

* read mime extensions

* Template plugins per page

* Cleanup

* Load allPlugins for the settings editor

* Expand on the comment

* Expand on comment

* Fix lint

Author: jtpio

.eslintignore

@@ -10,6 +10,7 @@ node_modules
 coverage
 *.map.js
 *.bundle.js
+app/index.template.js
 
 # jetbrains IDE stuff
 .idea/

.prettierignore

@@ -8,3 +8,4 @@ node_modules
 **/labextension
 build
 CHANGELOG.md
+app/index.template.js