chore(server): add github app install script for dev iteration against staging github app

[easyCZ]

Description

Moves the script from internal documentation into the repository for ease of use. This is needed to be able to iterate on github app integration locally/in dev.

Related Issue(s)

How to test

Release Notes

NONE

Documentation

[codecov]

Codecov Report

Merging #8591 (ea874f2) into main (3063396) will decrease coverage by 18.35%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             main    #8591       +/-   ##
===========================================
- Coverage   29.53%   11.17%   -18.36%     
===========================================
  Files         113       18       -95     
  Lines       18177      993    -17184     
===========================================
- Hits         5369      111     -5258     
+ Misses      12349      880    -11469     
+ Partials      459        2      -457     

Flag	Coverage Δ
components-content-service-app	?
components-content-service-lib	?
components-gitpod-cli-app	11.17% <ø> (ø)
components-image-builder-mk3-app	?
components-local-app-app-darwin-amd64	?
components-local-app-app-darwin-arm64	?
components-local-app-app-linux-amd64	?
components-local-app-app-linux-arm64	?
components-local-app-app-windows-386	?
components-local-app-app-windows-amd64	?
components-local-app-app-windows-arm64	?
components-supervisor-app	?
components-ws-daemon-app	?
components-ws-daemon-lib	?
components-ws-manager-app	?
components-ws-proxy-app	?
install-installer-raw-app	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
components/ws-daemon/pkg/content/tar.go
components/ws-manager/pkg/manager/manager_ee.go
components/ws-manager/pkg/manager/probe.go
components/ws-daemon/pkg/content/archive.go
components/supervisor/pkg/terminal/ring-buffer.go
components/ws-manager/pkg/manager/annotations.go
components/ws-proxy/pkg/proxy/pass.go
components/content-service/pkg/storage/storage.go
components/content-service/pkg/storage/gcloud.go
...s/content-service/pkg/service/ideplugin-service.go
... and 85 more

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[geropl]

LGTM