Missing support for fixed-size arrays

[alexdupre]

Running mars on a contract with a fixed-size array function parameter (e.g. address[2]) generates the following error:

Unknown type address[2]

Related code: https://github.com/TrueFiEng/Mars/blob/master/packages/mars/src/generate/generator.ts#L82-L107

[marcin-trust]

Thx for reporting this and details! Marking this bug as we do support dynamic-size arrays so fixed-size should be first-class citizen too.