Implement color get brightness & create blank image

[mee-ironsoftware]

Description

• Add AnyBitmap constructor to creating blank image

  var bitmap = new AnyBitmap(8, 8);
  bitmap.SaveAs("blank_bitmap.jpg");

• Add GetBrightness to calculates the brightness of a color.

  Color color = Color.Black;
  double brightness = color.GetBrightness();

Fixes #(issue number) If this PR addresses an existing issue, mention the issue number here.

Type of change

Please select the relevant option by placing an 'x' inside the brackets, like this: [x].

• [ ] 🐛 Bug fix (non-breaking change which fixes an issue)
• [X] ✨ New feature (non-breaking change which adds functionality)
• [ ] 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] 🏗️ Internal/structural update (non-breaking change that improves code quality, organization, or performance)
• [ ] 📚 This change requires a documentation update
• [ ] 🚀 DevOps build chain modification for release
• [ ] 🤖 DevOps build chain modification for CI

How Has This Been Tested?

Add unit tests to test each function.

Checklist:

Please run through the checklist as much as possible and mark the items completed by placing an 'x' inside the brackets, like this: [x].

• [X] My code follows the style guidelines of this project
• [X] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [X] My changes generate no new warnings
• [X] I have added tests that prove my fix is effective or that my feature works
• [X] New and existing unit tests pass locally with my changes
• [X] I have successfully run all unit tests on Windows
• [X] I have successfully run all unit tests on Linux