Add string interpolation support

[alexdovzhanyn]

We currently don't support string interpolation in Theta. Lets add string interpolation in, following the format:

name<String> = 'Bob'

outPut<String> = 'Hello my name is #{name}!'

We can do this directly in the parser. For each string that gets parsed, we can search through it and, if any interpolation is found, convert it to a BinaryOperationNode. in this way, the interpolation will just be syntactic sugar over string concatenation.

The above example should be converted to an AST matching the following structure:

BinaryOperationNode
  left:
    StringLiteralNode 'Hello my name is '
  right:
    BinaryOperationNode
      left:
        IdentifierNode
          name
      right:
        StringLiteralNode '!'

• Update the parser to reinterpret strings with interpolation into string concatenation
• Write a test to ensure string interpolation works

[PranavKeshav24]

Please assign this issue to me. I would be very happy to work on it.

[Probatio-Diabolica]

Hii Alex can you please assign this to me. thanks

[alexdovzhanyn]

@Probatio-Diabolica assigned!