Add bitmap, sound effect and music unit tests

[matt439]

Description

There is currently only two unit tests: JSON and text. There are many other processes which could be tested such as audio, images. I have created three unit tests which cover bitmaps, sound effects and music. They each perform exhaustive testing of the types including their loading and freeing.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as
  expected)
• Documentation (update or new)

How Has This Been Tested?

Adding the new tests was achieved by running cmake -G "Unix Makefiles" . followed by make when in the /splashkit-core/projects/cmake directory. The tests deliberately cause warning messages to occur in the terminal when they attempt to load non-existent files.

Testing Checklist

• Tested with sktest
• Tested with skunit_tests

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have requested a review from ... on the Pull Request

[Wills2022]

Hi Matthew,

Thanks for updating the pull. I've re-tested this locally using the instructions you've provided and i'm now able to get the new unit-tests to run.

I noticed that you've already incorporated the other changes i'd requested in the original pull. Otherwise, looks good !

[Liquidscroll]

Look good to me! I also ran these tests and got the expected output. It's always great to see more thorough testing :)

[WhyPenguins]

Looks good! Nice work 😃