fix: do not panic linting files with UTF-8 BOM

[dsherret]

Closes #24122

[dsherret]

---- specs::lint::bom ----
command V:\deno\target\debug\deno.exe lint mod.ts
command cwd V:\deno\tests\specs\lint\bom
output path V:\deno\tests\specs\lint\bom\mod.out

panicked at tests\specs/mod.rs:391:12:
assertion failed: `(left == right)`

Diff < left / right > :
<
<============================================================
<Deno has panicked. This is a bug in Deno. Please report this
<at https://github.com/denoland/deno/issues/new.
<
<Platform: windows x86_64
<Version: 1.44.1
<Args: ["V:\\deno\\target\\debug\\deno.exe", "lint", "mod.ts"]
<
<thread 'tokio-runtime-worker' panicked at V:\.cache\cargo\registry\src\index.crates.io-6f17d22bba15001f\dprint-swc-ext-0.16.0\src\common\pos.rs:348:3:
<byte index 84 is out of bounds of `// this file is saved as UTF8 with BOM
<console.log("Hello, world!");
<
<const t = 5;
<`
<note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[bartlomieju]

LGTM