UI: Add warning for non-NV12 color formats

Non-NV12 video formats are primarily intended for recording.  For
streaming, if the libobs color format is not set to NV12, it's likely
that the video frames will have to be converted to NV12, which will use
extra CPU usage.  Due to that fact, it's important to warn the user of
that potential extra increased CPU usage that may be required when
streaming.

obs/forms/OBSBasicSettings.ui

@@ -2518,6 +2518,22 @@
                   <property name="text">
                    <string notr="true"/>
                   </property>
+                  <property name="wordWrap">
+                   <bool>true</bool>
+                  </property>
+                 </widget>
+                </item>
+                <item>
+                 <widget class="QLabel" name="advancedMsg2">
+                  <property name="styleSheet">
+                   <string notr="true">color: rgb(255, 0, 4);</string>
+                  </property>
+                  <property name="text">
+                   <string notr="true"/>
+                  </property>
+                  <property name="wordWrap">
+                   <bool>true</bool>
+                  </property>
                  </widget>
                 </item>
                </layout>