[FIX] Move all implementation under include guard

[dario-loi]

All function implementations are now under the #ifdef FBGL_IMPLEMENTATION guard, in order to prevent bugs as described by #3 (fixes task 3)

Commit also solves a double #define on the FBGL_MAX_KEYS marcro. My formatter ran on the code and sorted the includes as well as applied general formattings to everything, if you want I can amend the commit with just the relevant update (and switch the formatter off)

[lvntky]

I think formatter off commit would be better since i could not understand which lines are changed. And i also love linux c style provided by .clang-format 😂

[dario-loi]

Ohhh I did not see the .clang-format file there, however, I am now running clang-format --style=file -i ./example/** and the resulting files are still different from the ones on the repo. Can you try to format yourself in a commit to see if we can get the diffs to go away?

[lvntky]

Ohhh I did not see the .clang-format file there, however, I am now running clang-format --style=file -i ./example/** and the resulting files are still different from the ones on the repo. Can you try to format yourself in a commit to see if we can get the diffs to go away?

Sure I will open up a formatted pr to your repo

[lvntky]

Apparently, I cannot fork your repo since I already have an fbgl repo. but we can do it this way. I will open a branch called dev for you, not master, and you will assign your commit to the dev branch, and I will format the files in dev and merge them to the master branch. Or you can format it yourself using clang-format.

here is the formatting process:

1. you have to download the clang-format first. For arch based systems its: sudo pacman -S clang
2. go to the root dir
3. and just type: clang-format -i fbgl.h
   @dario-loi

[lvntky]

LGTM, thank you !