Moved outside BeginDrawing()/EndDrawing() to illustrate drawing is happening to an external texture (not screen)

* Added support for additional mouse buttons

* Renamed mouse button enum

Co-authored-by: Lambert Wang <lambert.ww@gmail.com>

Some enums values have been renamed to be more consistent and also provide a more detailed description:
 - ShaderLocationIndex:    LOC_VERTEX_POSITION -> SHADER_SHADER_LOC_VERTEX_POSITION
 - ShaderUniformDataType:  UNIFORM_VEC2 -> SHADER_UNIFORM_VEC2
 - MaterialMapType: MAP_ALBEDO -> MATERIAL_MAP_ALBEDO
 - PixelFormat: UNCOMPRESSED_GRAYSCALE -> PIXELFORMAT_UNCOMPRESSED_GRAYSCALE

This function was renamed for consistency in raylib 3.0, just unified all examples to use TextFormat() instead of FormatText()

Now shader uses `fragTexCoord` that are the full screen texture coordinates normalized, instead of `gl_fragCoord`, the unnormalized screen coordinates

Also changed path to shader back to what it was originally.

Now dividing by the zoom instead of multiplying (in the shader), so zoom works as expected. Also zoom increase/decrease is now scaled depending on the current zoom.

Redesigns, deletes and renames

Also noted authors propertly on contributed examples