[Feature Request]: Support Strong Etag Generation

[samuel871211]

Problem

Currently, send always generates weak ETags for file stats. Some use cases require strong ETags for better HTTP caching semantics.

Proposed Solution

Add an option to generate strong ETags based on file stats:

send(req, path, { 
  etag: { weak: false }  // strong ETag
})

We can modify the source code as below

var val = etag(stat, { weak: this._etag.weak })
...

Implementation preserves backward compatibility

etag: true → continues to generate weak ETags (unchanged)
etag: { weak: false } → generates strong ETags
etag: { weak: true } → generates weak ETags
etag: false → disables ETag generation (unchanged)

Would you be interested in this enhancement? I'm happy to contribute to the implementation.