Add L5 principles statement

[lee2sman]

L5 is an implementation of Processing in Lua using the Love2d framework. Lua and Love2d were chosen for distinct reasons. Our development choices are guided by Processing/p5 but also permacomputing principles. Just as p5.js has its Access statement that guides its development, we should have a Principles Statement that provides scope and guides our design decisions.

[lee2sman]

To be clear, L5 has been built from the beginning this way, but it should be spelled out explicitly.