Improves error message for imbalanced tokens.
```
× Expected `,` or `]` but found `const`
╭─[misc/fail/imbalanced-array-expr.js:2:1]
1 │ const foo = [0, 1
· ┬
· ╰── Opened here
2 │ const bar = 2
· ──┬──
· ╰── `,` or `]` expected
╰────
```
The error message for this case was:
```
x Expected `,` but found `const`
,-[:2:1]
1 | const foo = [0,1
2 | const bar = 2
: ^^|^^
: `-- `,` expected
`----
```
This change makes it clear why the parser is expecting `,` and also tell that it can be fixed by adding the closing token somewhere.
sapphi-red