Install translations in PACKAGE MODE

[Nenderus]

Description of Changes

Installs localization files when the PACKAGE_MODE option is enabled

Rationale behind Changes

If you use the PACKAGE_MODE option, the localization files still have to be placed in the translations folder relative to the pcsx2-qt binary file, which is unacceptable for packaging in a package for Linux

Suggested Testing Steps

Run with a locale other than en_US and make sure that the interface uses the correct locale

[github-actions]

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[weirdbeardgame]

Sorry, was working on fixing that bit. Thanks for the PR :)

[F0bes]

Changes are good, can you please prefix your commit though. Something like CMake: or Translations: will do.

[Nenderus]

Changes are good, can you please prefix your commit though. Something like CMake: or Translations: will do.

Done