Add descriptions

[Freeman-Trader]

Add descriptions for classes, methods, properties, and global objects.

[j20001970]

Hi, there is currently a WIP classes documentations on dev branch, but the progress is stalled due to me working on personal stuff recently. If things went smoothly it will be merged in master branch in a few days.

[j20001970]

Hi, just a heads up: Class documentations has been merged in 0b6c1a8. Some places might still need improvement, but it should give users a bit better idea on what components GDMP provides.

[Freeman-Trader]

Thank you, I really appreciate it 😄