[#62358298]

* open-linux-62358298:
  Add Linux open
Merge branch 'master' into manifest-missing-file-62423444
Add support for custom.css

[#62802682]
Get custom.css working with local server

[Delivers #62802682]
Merge branch 'master' into custom-css-62802682
Merge branch 'master' into manifest-missing-file-62423444
Merge branch 'manifest-missing-file-62423444' into custom-css-62802682
Fix an EPUB validation error

[#62802682]
[#62802682]

* custom-css-62802682:
  Fix an EPUB validation error
  Get custom.css working with local server
  Add support for custom.css