NEON725

Added unused variable to embedded lighting.frag shader in Lesson 7.

2

While following the [Lesson 7 Tutorial](https://taidaesal.github.io/vulkano_tutorial/section_7.html), I encountered a particularly nasty gotcha-moment that relates to the way the GLSL compiler tries to optimize-away unused variables. In the intermediary stages of...

Single-character typo in the header for Lesson 0.