feat(api): make FreeType a toggleable option which is disabled by default (#254)

* deps(build): bump FreeType from 2.12.1 to 2.13.3

* fix(generator): add missing ImGuiFreeTypeBuilderFlags

* feat(generator): add possibility to provide additional defines specifically for AST

* feat(api): make FreeType optional and disabled by default

FreeType renderer is still included in the final build.
Its usage is toggleable and DISABLED by default.

buildSrc/scripts/vendor_freetype.sh

@@ -17,7 +17,7 @@ echo "Vendor type set to '$VTYPE'"
 
 # Define library directory and version
 LIBDIR=build/vendor/freetype
-VERSION=2.12.1
+VERSION=2.13.3
 
 # Clean and create library directory, then extract FreeType source
 echo "Cleaning and creating library directory, then extracting FreeType source..."