Add frozen string literal magic comment (potential breaking change)

[tagliala]

This cop was disabled probably by mistake, since it is present in both Arbre and Active Admin gems

The only production code affected is:

• app/controllers/inherited_resources/base.rb
• lib/inherited_resources/version.rb

Change to version.rb is safe.

After inspecting the source code of InheritedResources module, the change seems safe, but it can represent a breaking change in third-party application.

Since we are bumping the major version number, it would be fine to break if documented.

Fixed with rubocop -A

Also adds Style/Encoding cop for parity with Arbre

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.92%. Comparing base (fdc9a9c) to head (cb1bc19). Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #933 +/- ## ======================================= Coverage 98.92% 98.92% ======================================= Files 14 14 Lines 557 557 ======================================= Hits 551 551 Misses 6 6 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.