chore(apps): move icons into the apps folder (#3139)

* chore(apps): move icons into the apps folder

* rename to `icon.png`

* replace solr image

* remove `docs/` from gitignore

* move app specific docs into app folder [skip ci]

* fix some links

* chore(apps): update image links temporary

charts/stable/jdownloader2/docs/installation_notes.md

@@ -0,0 +1,8 @@
+# Installation Notes
+
+- If you enable `Ingress` for this app, you need to have `SECURE_CONNECTION` set to `false` and `Port Type` set to `HTTP`, otherwise you may run into errors for `Too many redirects`.
+- `VNC` can't be `Ingressed`. if you want to use `VNC`, you must set this service to `Simple` instead of `clusterIP`.
+- `VNC` with `SECURE_CONNECTION` set `true`, only works with very few clients. One of them is `SSVNC`.
+- `SECURE_CONNECTION` affects both `WebUI` and `VNC`.
+
+- If you are passing through devices such as `Optical Drives`, you have to Click `Container Security Settings` and set `PUID` to `0`.