Fix: Issue 1887 (#1892)

* Value setting Stateful toolbar buttons derive from base class

* Rename base class as QuillToolbarBaseValueButton

* Removed deprecated functions

* Move clipboard actions to QuillController

* Fix: collectAllIndividualStylesAndEmbed for result span

* Add: Clipboard toolbar buttons

* Add: test for QuillController clipboard
Dart Formatted

* Fix Issue 1887

---------

Co-authored-by: Douglas Ward <dward@scied.com>

lib/src/models/rules/insert.dart

@@ -565,8 +565,8 @@ class PreserveInlineStylesRule extends InsertRule {
 
     if ((prev.data as String).endsWith('\n')) {
       if (prev.attributes != null) {
-        for (final value in prev.attributes!.values) {
-          if (!(value as Attribute).isInline) {
+        for (final key in prev.attributes!.keys) {
+          if (!Attribute.inlineKeys.contains(key)) {
             return null;
           }
         }