Add EditorConfig

[wb9688]

What is it?

• Bug fix (user facing)
• Feature (user facing)
• Code base improvement (dev facing)
• Meta improvement to the project (dev facing)

Description of the changes in your PR

This PR adds an EditorConfig. EditorConfig is some standard to set certain code style related settings in different editors and IDEs. I've also changed all files (except gradlew.bat) to use LF line ending, replaced all tabs with 4 spaces, have a newline at the end, and to not have trailing whitespace. I didn't look at whether files that were formatted with spaces are actually formatted with 4 spaces, or whether the indentation is correct.

Agreement

• I carefully read the contribution guidelines and agree to them.

[Stypox]

I like those rules. I'm a little bit worried if changing all of the strings.xml files could cause problems with weblate. Also, is it ok to edit changelogs of older versions (I assume it is, I'm pointing out this just to make sure)? Other than that I think this can be merged.

[wb9688]

I'm a little bit worried if changing all of the strings.xml files could cause problems with weblate.

Maybe, cc @B0pol and @TobiGr. There are some issues that could actually be fixed through Weblate, however some others have to be fixed this way. I also noticed that some translations don't have %1$s and similar written correctly, however I didn't fix those. ^{And I had to laugh when I saw the Flemish translation.}

Also, is it ok to edit changelogs of older versions (I assume it is, I'm pointing out this just to make sure)?

Yes, F-Droid only looks at the changelog in the commit that was tagged for that release.

[B0pol]

I've a question: does this automatically set the rule for imports? Because often you remove the wildcard imports .*. But as it's automatically done by intellij, people revert that.
If it's possible to configure imports, please do it.

[wb9688]

@B0pol: No, that's not possible in EditorConfig, as that's some IntelliJ-specific setting, however we could add ij_java_class_count_to_use_import_on_demand = 999 and ij_java_names_count_to_use_import_on_demand = 999 and whatever the Kotlin setting is to it as IntelliJ supports their own non-standard settings in EditorConfig, which is technically invalid, but other EditorConfig implementations ignore it anyway, so we could safely add it. You could also manually set it in Settings -> Editor -> Code Style -> Java -> Imports, and we enforce not using wildcard imports through Checkstyle and Ktlint, and having alphabetically sorted imports in Kotlin through Ktlint (which IntelliJ doesn't do fully automatically, though that will be fixed by JetBrains/kotlin#3336 and for now we can just manually run the formatKtlint task when writing Kotlin).