add `let assert`

[inoas]

❯ ./scripts/integration_test.sh
Running parser against gleam-lang/stdlib
Total parses: 45; successful parses: 45; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/json
Total parses: 3; successful parses: 3; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/http
Total parses: 10; successful parses: 10; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/example-todomvc
Total parses: 23; successful parses: 23; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/bitwise
Total parses: 2; successful parses: 2; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/erlang
Total parses: 13; successful parses: 13; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/otp
Total parses: 13; successful parses: 13; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/cowboy
Total parses: 3; successful parses: 3; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/hackney
Total parses: 2; successful parses: 2; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/httpc
Total parses: 2; successful parses: 2; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/elli
Total parses: 4; successful parses: 4; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/javascript
Total parses: 7; successful parses: 7; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/example-echo-server
Total parses: 5; successful parses: 5; failed parses: 0; success percentage: 100.00%

Running parser against gleam-lang/plug
Total parses: 2; successful parses: 2; failed parses: 0; success percentage: 100.00%

[J3RN]

Closed in favor of #50