[IDEA] Dark mode

[rogin]

Is your feature request related to a problem? Please describe.
I'm migrating popular requests from NextGen's repo. This was issue #4478

I'd like the option to enable dark mode. Automatic detection of system-wide settings would be ideal.

Describe your use case
I need this feature so I can avoid vision strain.

Describe the solution you'd like
Reads the OS setting out of the box. Have a setting or two to force enable/disable it.

Describe alternatives you've considered
None

Additional context
I forgot who referenced jSystemThemeDetector for this, but it looks like a clear and simple integration option. However, it requires Java 11 or higher.

[rogin]

Detecting dark mode seems easy. It's the visual change that'll require the effort. The two options mentioned here seemed promising. Can't do much now until the codebase is migrated to Java 9+ modules.

For jSystemThemeDetector dependencies, since we don't yet have maven or gradle, configure a dummy pom.xml then run mvn dependency:list. There were only a handful.

[rogin]

Here's the maven dep list when creating a dummy app for jSystemThemeDetector v3.6:

[INFO] --- dependency:3.7.0:list (default-cli) @ my-app ---
[INFO]
[INFO] The following files have been resolved:
[INFO] com.github.Dansoftowner:jSystemThemeDetector:jar:3.6:compile -- module com.jthemedetector
[INFO] org.slf4j:slf4j-api:jar:1.7.30:runtime -- module org.slf4j [auto]
[INFO] net.java.dev.jna:jna:jar:5.8.0:runtime -- module com.sun.jna [auto]
[INFO] net.java.dev.jna:jna-platform:jar:5.8.0:runtime -- module com.sun.jna.platform [auto]
[INFO] de.jangassen:jfa:jar:1.1.9:runtime -- module jfa
[INFO] com.github.oshi:oshi-core:jar:5.7.1:runtime -- module com.github.oshi [auto]
[INFO] io.github.g00fy2:versioncompare:jar:1.4.1:runtime -- module versioncompare (auto)
[INFO] org.jetbrains:annotations:jar:19.0.0:runtime -- module org.jetbrains.annotations [auto]