Add "hugo mod npm pack"

This commit also introduces a convention where these common JS config files, including `package.hugo.json`, gets mounted into:

```
assets/_jsconfig
´``

These files mapped to their real filename will be added to the environment when running PostCSS, Babel etc., so you can do `process.env.HUGO_FILE_TAILWIND_CONFIG_JS` to resolve the real filename.

But do note that `assets` is a composite/union filesystem, so if your config file is not meant to be overridden, name them something specific.

This commit also adds adds `workDir/node_modules` to `NODE_PATH` and `HUGO_WORKDIR` to the env when running the JS tools above.

Fixes #7644
Fixes #7656
Fixes #7675

modules/config.go

@@ -56,7 +56,9 @@ func ApplyProjectConfigDefaults(cfg config.Provider, mod Module) error {
 	// the basic level.
 	componentsConfigured := make(map[string]bool)
 	for _, mnt := range moda.mounts {
-		componentsConfigured[mnt.Component()] = true
+		if !strings.HasPrefix(mnt.Target, files.JsConfigFolderMountPrefix) {
+			componentsConfigured[mnt.Component()] = true
+		}
 	}
 
 	type dirKeyComponent struct {
@@ -318,12 +320,21 @@ type Mount struct {
 	Target string // relative target path, e.g. "assets/bootstrap/scss"
 
 	Lang string // any language code associated with this mount.
+
 }
 
 func (m Mount) Component() string {
 	return strings.Split(m.Target, fileSeparator)[0]
 }
 
+func (m Mount) ComponentAndName() (string, string) {
+	k := strings.Index(m.Target, fileSeparator)
+	if k == -1 {
+		return m.Target, ""
+	}
+	return m.Target[:k], m.Target[k+1:]
+}
+
 func getStaticDirs(cfg config.Provider) []string {
 	var staticDirs []string
 	for i := -1; i <= 10; i++ {