* Flow enums parsing
* Parse exporting enums
* Enums parsing remove lookahead, other improvements
* Enums: add EnumBody and EnumMember aliases, change boolean members to use BooleaLiteral value
* Fix enum member init flow type, now that boolean members have a BooleanLiteral value
* Flow enums: use contextual utils, change members length checks to use logic operators, remove reserved word logic modification
* Flow enums: remove unnecessary code in generator, fix error message
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