Replace GLEW with GLAD

[adam4813]

Closes #93

Description

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[adam4813]

I cannot test context creation on linux/mac, but it should be a drop-in replacement.

[adam4813]

TODO: Add GLAD install instructions for non-vcpkg users OR just include the static core generated file