v2: breaking changes list / add norns-compat.lua

[robbielyman]

incrementing a major version number is the time to do this sort of shakeup, and i'm feeling like it's overdue

i'll pin this and add to it as i break more things

• minimal impact on global namespace: e.g. grid is now seamstress.monome.grid, osc is now seamstress.osc, &c.
• style: follows Zig's lead: variables, (including some functions-as-variables bc Lua is loosey-goosey and they felt right) are / remain snake_case. functions should now be camelCase. types (including type-names-as-constructor-functions) are PascalCase. avoid SCREAMING_SNAKE_CASE.

would be great to have a norns_compat.lua file under lib so that folks interested in using seamstress as an extension platform for norns can use if seamstress then require('lib.norns_compat') end