[Docs] Standardise and Enforce readme structures

[Ornias1993]

Is your feature request related to a problem? Please describe.
For reviewers it's increasingly hard to review if everyone has their own readme.md format.
We also should stop using upstream readme.md files, because they (obviously) don't reflect our project.

Describe the solution you'd like
Standardise the readme format and rework all readme's accordingly.
Enforce if needed,

Describe alternatives you've considered
Leaving it up to individual app maintainers.
However: in some cases, such as common-chart updates, other developers than app maintainers would need to make bulk-changes or review things anyway.

[truecharts-admin]

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