Themes and plugins are not recognized when edited and the line breaks are saved as "\r".

[azaozz]

This can happen if the user has old Mac that runs MacOS < 10. Seems some of the browsers of that time use the native \r line end format.

Solution seems to be to normalize line breaks when saving edited theme and plugin files, all current browsers seem to work well with \n.

[azaozz]

Related: #9716.

[solarissmoke]

#19854