prefill new style name with the domain/hostname

implements #344

edit/edit.js

@@ -225,7 +225,9 @@ function initStyleData() {
   const id = params.get('id');
   const createEmptyStyle = () => ({
     id: null,
-    name: '',
+    name: params.get('domain') ||
+          tryCatch(() => new URL(params.get('url-prefix')).hostname) ||
+          '',
     enabled: true,
     sections: [
       Object.assign({code: ''},

edit/source-editor.js

@@ -106,7 +106,10 @@ function createSourceEditor(style) {
     }
     const DEFAULT_CODE = `
       /* ==UserStyle==
-      @name           ${t('usercssReplaceTemplateName') + ' - ' + new Date().toLocaleString()}
+      @name           ${
+        style.name ||
+        t('usercssReplaceTemplateName') + ' - ' + new Date().toLocaleString()
+      }
       @namespace      github.com/openstyles/stylus
       @version        0.1.0
       @description    A new userstyle