I needed to do a variety of things to ensure cxxopts worked well in my own project.
I created a new cmake module to abstract a lot of the logic in the main CMakelists.txt, I think it really assists in the readability of the project. Consequently a lot of logic is now written in functions.
I tested logic locally with cmake 3.19
I made a lot of the project options off by default unless the project is being built standalone. As a frequent consumer of cmake libraries this is a huge issue. Since examples, tests, installation, etc. aren't things I expect/desired by default when using libraries.
Other than that it's just minor nitpicks.
