Lex `fn` as `FN`
Lex `end` as `END`
Lex `true` as `TRUE`
Add TRUE to accessExpression
Lex `false` as `FALSE`
Add `FALSE` to `accessExpression`
Lex `nil` as `NIL`
Add `NIL` to `accessExpression`
Add Regular Keywords to README
Lands #72, Regular Keywords
Update changelogs