Auto merge of #12545 - jeremyBanks:shebangs, r=Veykril

fix: inserted imports must come after a shebang if present

The current `insert_use` logic adds the first `use` item near the beginning of the file, only skipping past comments and whitespace. However, it does not skip leading [shebang lines](https://en.wikipedia.org/wiki/Shebang_\(Unix\)). This can produce a syntax error, as shebangs are only accepted (ignored) on the first line of the file.

### Before Insertion (valid syntax)

```rust
#!/usr/bin/env rust

fn main() {}
```

### After Insertion (invalid syntax)

```rust
use foo::bar::Baz;

#!/usr/bin/env rust

fn main() {}
```

Rust analyzer's grammar is already shebang-aware, so this PR just adds that to the array of SyntaxKinds that are skipped past when looking for an insertion location, and adds a corresponding test case.

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