rmodels.c, LoadImageFromCgltfImage() : fix base64 padding support (#4112)

* rmodels.c, LoadImageFromCgltfImage() : fix base64 padding support

This should fix the issue related to `.gltf` embeded image in base64 format, by ignoring `=` padding and calculating the data size in bytes correctly.

* follow guidelin convention

* try to follow guideline convention as much as possible

* clarify comments

i hope it's clear ennough

Author: SuperUserNameMan

src/rmodels.c

@@ -4815,7 +4815,9 @@ static Image LoadImageFromCgltfImage(cgltf_image *cgltfImage, const char *texPat
             else
             {
                 int base64Size = (int)strlen(cgltfImage->uri + i + 1);
-                int outSize = 3*(base64Size/4);         // TODO: Consider padding (-numberOfPaddingCharacters)
+                while (cgltfImage->uri[i + base64Size] == '=') base64Size--;    // Ignore optional paddings
+                int numberOfEncodedBits = base64Size*6 - (base64Size*6) % 8 ;   // Encoded bits minus extra bits, so it becomes a multiple of 8 bits
+                int outSize = numberOfEncodedBits/8 ;                           // Actual encoded bytes
                 void *data = NULL;
 
                 cgltf_options options = { 0 };