[docs-only] docs: first draft of the custom apps in ocis and web blog post, part-1

[fschade]

it contains a good start for part 1, it needs some better writing here and there, should be enough as a starting point.

toDos:

• [ ] part-1: app basics, what it is, why you need it
  • [X] basic article
  • [ ] text correction and better wording
• [ ] part-2: write and ship a basic custom extension
  • [ ] basic article
  • [ ] text correction and better wording
  • [x] docker app dev example and sandbox
• [ ] part-3: advanced techniques and web-app sdk deep dive
  • [ ] basic article
  • [ ] text correction and better wording

@tbsbdr lets discuss the next steps

[update-docs[bot]]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[mmattel]

@phil-davis I guess that a language review may be beneficial 😄

[fschade]

@mmattel many thanks for the text tunings, applied!

[fschade]

@dragotin can you check the latest graph, i think its more snappy now.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[fschade]

@tbsbdr can you check and take over, i start writing part two now

[mmattel]

FYI, @micbar has added most of the web-extensions to the ocis_full example.