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/unpackerr/Chart.yaml

@@ -9,7 +9,7 @@ description: This application runs as a daemon on your download host. It checks
   completed downloads and extracts them so Radarr, Lidarr, Sonarr, and Readarr may
   import them
 home: https://github.com/truecharts/apps/tree/master/charts/stable/unpackerr
-icon: https://truecharts.org/_static/img/appicons/unpackerr.png
+icon: https://truecharts.org/img/appicons/unpackerr.png
 keywords:
 - unpackerr
 - sonarr