feat: add simple binary operation type checking

[baszalmstra]

This PR basically adds checks to determine whether a binary operation is valid. This test should report an error:

fn foo() {
    let b = false;
    let n = 1;
    let _ = b + n; // error: invalid binary operation
}

[codecov]

Codecov Report

Merging #70 into master will not change coverage.
The diff coverage is 0%.

@@          Coverage Diff          @@
##           master    #70   +/-   ##
=====================================
  Coverage       0%     0%           
=====================================
  Files          81     81           
  Lines        5604   5628   +24     
=====================================
- Misses       5604   5628   +24

Impacted Files	Coverage Δ
crates/mun_hir/src/expr.rs	0% <0%> (ø)	⬆️
crates/mun_hir/src/ty/infer.rs	0% <0%> (ø)	⬆️
crates/mun_hir/src/ty/tests.rs	0% <0%> (ø)	⬆️
crates/mun_hir/src/ty/op.rs	0% <0%> (ø)	⬆️

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