Add nextcloud/coding-standard dependency

[docjyJ]

Add nextcloud/coding-standard

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Found 43 of 43 files that can be fixed in 4.645 seconds, 18.00 MB memory used
Script php-cs-fixer fix --dry-run --diff handling the cs:check event returned with error code 8

[docjyJ]

I split into 2 commits:

• b3c7cbe added bibliotech
• cad1a5a run the cs

[szaimen]

Thanks again for your contributions @docjyJ! I think this looks good but probably makes sense to wait for e.g. this PR: #4804 as otherwise it will be a rebase hell...

[docjyJ]

Yes, I know, complicated to merge. Since it's only style, it must not be the worst case.

I dropped the commit from run cs:fix and rebased the branch.