npm package registry support for bin (#21372)

Fix #21303

npm package.json supports binary packaging:
https://docs.npmjs.com/cli/v8/configuring-npm/package-json#bin

the npm registry documents that the binary references will be attached
to the abbreviated version object:

https://github.com/npm/registry/blob/master/docs/responses/package-metadata.md#abbreviated-version-object

unfortunately their api documentation leaves this out:
https://github.com/npm/registry/blob/master/docs/responses/package-metadata.md#abbreviated-version-objectdoc

which is likely to be the reason this was left out in gitea's initial
implementation

this response is critical for npm to install the binary in the `.bin`
folder so as to be included on the users default bin path, resulting in
immediate access to any binaries provided by the package

routers/api/packages/npm/api.go

@@ -67,6 +67,7 @@ func createPackageMetadataVersion(registryURL string, pd *packages_model.Package
 		PeerDependencies:     metadata.PeerDependencies,
 		OptionalDependencies: metadata.OptionalDependencies,
 		Readme:               metadata.Readme,
+		Bin:                  metadata.Bin,
 		Dist: npm_module.PackageDistribution{
 			Shasum:    pd.Files[0].Blob.HashSHA1,
 			Integrity: "sha512-" + base64.StdEncoding.EncodeToString(hashBytes),