Support minting new javascript resources

Currently an attempt to create a new javascript reource such as foo.js errors with the message "A new text file has to have an file extension like .txt .ttl .json etc".  These changes support files whose content-type  includes javascript.

Author: jeff-zucker

sourcePane.js

@@ -21,6 +21,7 @@ module.exports = {
       if (t.startsWith(prefix)) return 'Source'
       if (t.includes('xml')) return 'XML Source'
       if (t.includes('json')) return 'JSON Source' // Like eg application/ld+json
+      if (t.includes('javascript')) return 'Javascript Source';
     }
     return null
   },
@@ -42,7 +43,7 @@ module.exports = {
     const contentType = mime.lookup(newInstance.uri)
     if (
       !contentType ||
-      !(contentType.startsWith('text') || contentType.includes('xml') || contentType.includes('json'))
+      !(contentType.startsWith('text') || contentType.includes('xml') || contentType.includes('json') || contentType.includes('javascript')
     ) {
       const msg =
         'A new text file has to have an file extension like .txt .ttl .json etc.'