Document how to reset the parser after using feed

[gajus]

const parser = new Parser(commandGrammar.ParserRules, commandGrammar.ParserStart);

const results = parser.feed(command).results;

How to reset the parser after feeding it some data?

[kach]

The easiest way is to just make a new parser.

[gajus]

Not the most efficient way, though.

It would be nice to have a simple "reset" function.

[tjvr]

Now the most efficient way, though.

It's actually very cheap.