Tweak the light syntax highlighting theme colors to look like the Godot script editor's default light theme

**Your Godot version:**
3.2.3.stable
**Issue description:**
It could be confusing or is just sad that functions are not shown highlighted as they are in the Editor. Since the documentation examples are there for showing how the Editor works, they should look equal as far as possible.
**URL to the documentation page (if already existing):**
all with code