Lexing and Parsing errors should throw a SyntaxError

[HalidOdat]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Any invalid syntax like {.

Expected behavior
The expected behavior would be a SyntaxError with the parser error.

Actual behavior
we get a panic with the message.

Additional context
I think the best way to implement this would be to have the lexer and parser, generate the error as we do now but not panic, and in forward we check if lexing or parsing failed and then throw a SyntaxError, this would eliminate the need to introduce the Interpreter to the lexer/parser which would keep the code cleaner.

This is blocked until #536 lands

[Razican]

Hmmm this is interesting, where do we panic? I thought we just returned a parsing/lexing error.

[HalidOdat]

Hmmm this is interesting, where do we panic? I thought we just returned a parsing/lexing error.

Sorry about that, we don't panic but we print the parsing error and exit https://github.com/boa-dev/boa/blob/master/boa/src/lib.rs#L83-L85

[Razican]

Hmmm this is interesting, where do we panic? I thought we just returned a parsing/lexing error.

Sorry about that, we don't panic but we print the parsing error and exit /boa/src/lib.rs@master#L83-L85

True, that should throw a Syntax Error :)