Add some disclaimer text to the schemes page (#12663)

People get confused about this. This should help. It doesn't really fix it, but it should help.

* [x] Does enough for #9775 to get it out of 1.14
* [x] I work here
* [x] Screenshot below.

![image](https://user-images.githubusercontent.com/18356694/157732913-86f0af51-8c37-4827-9d21-5775d0bfdeb7.png)

* [ ] todo: Discuss the text here. @cinnamon-msft this sound good?

(cherry picked from commit 460a991)

src/cascadia/TerminalSettingsEditor/ColorSchemes.xaml

@@ -98,6 +98,10 @@
                     Margin="{StaticResource StandardIndentMargin}"
                     Spacing="24">
 
+            <TextBlock x:Uid="ColorSchemesDisclaimer"
+                       Margin="{StaticResource StandardIndentMargin}"
+                       Style="{StaticResource DisclaimerStyle}" />
+
             <!--  Select Color and Add New Button  -->
             <StackPanel Margin="0,5,0,0"
                         Orientation="Horizontal">

src/cascadia/TerminalSettingsEditor/Resources/en-US/Resources.resw

@@ -1222,6 +1222,10 @@
     <value>Cancel rename</value>
     <comment>Text label for a button that can be used to cancel a rename operation during the renaming process.</comment>
   </data>
+  <data name="ColorSchemesDisclaimer.Text" xml:space="preserve">
+    <value>Schemes defined here can be applied to your profiles under the "Appearances" section of the profile settings pages.</value>
+    <comment>A disclaimer presented at the top of a page. "Appearances" should match Profile_Appearance.Header.</comment>
+  </data>
   <data name="Profile_BaseLayerDisclaimer.Text" xml:space="preserve">
     <value>Settings defined here will apply to all profiles unless they are overridden by a profile's settings.</value>
     <comment>A disclaimer presented at the top of a page. See "Nav_ProfileDefaults.Content" for a description on what the defaults layer does in the app.</comment>