Help: Added explaining note to preferences dialog (#15115)

* Help: Added explaining note to preferences dialog - fixes #14922

* Help: Fixed typos

src/Mod/Help/dlgPreferencesHelp.ui

@@ -164,6 +164,16 @@ custom stylesheet below and can look nicer than the wiki option. The 'Markdown'
       <string>Display</string>
      </property>
      <layout class="QVBoxLayout" name="verticalLayout_3">
+      <item>
+       <widget class="QLabel" name="label_3">
+        <property name="text">
+         <string>Note: if PySide Web components are not found on your system, help pages will open in your default web browser regardless of the options below</string>
+        </property>
+        <property name="wordWrap">
+         <bool>true</bool>
+        </property>
+       </widget>
+      </item>
       <item>
        <widget class="Gui::PrefRadioButton" name="radioBrowser">
         <property name="toolTip">