feat: (wip) parse function call expressions and assign statements

feat: handle short if statement in parser, typer and C codegen

feat: handle while loop in parser, typer and C codegen

feat: integrate unit walker into builder

feat: walk imports during in builder

feat: parse import blocks

feat: handle ref type in parser, typer and C codegen

feat: parse type definitions and index them in typer

feat: handle strings in parser, typer and C codegen, typecheck branch conditions

feat: compile generated C code via native cc

feat: handle span num field select in parser, typer and C codegen

feat: simple usage checks for local symbols

feat: span types in parser and typer, simple exit flow analysis

feat: simple type checking for return statements and binary expressions

feat: handle if statement in parser, typer and C codegen

feat: handle function stubs in parser, typer and C codegen

feat: handle block constants in parser, typer and C codegen

refact: syncronization after parsing errors

feat: handle parenthesis and binary expression precedence in C codegen

feat: use strings for storing source texts in memory to avoid allocations in lexer

feat: handle symbol and parenthesis expressions in parser, typer and C codegen