Add very little sanitization to indentifier names in ExportDataAsCode()

[Dev-Tade]

Hello, I decided to add this little sanitization for the '-' characater to the exported identifiers since find it quite useful for me and may help to other raylib users that use '-' in their file names.

Without this change any exported data to a file name containing the character would not compile since it's not a valid character for identifiers, I could have added more characters to be replaced ('@', '#', '%', etc) but i don't think they are really used for the use cases of ExportDataAsCode().

Thanks for your time ❤️

[raysan5]

@Dev-Tade Thanks for the review, I was a bit reticent about this change but I will merge this one. Still, it will require some review and also alignment wit all the other Export*AsCode() functions in raylib.

[Dev-Tade]

I was thinking on adding a function for converting the name to uppercase and also sanitize so it could be reusable but didn't feel like, since my problem was with DataAsCode but I agree the other variants of exporting as code would need review and possibly require sanitization.