docs: adds css variable type cleanup step

Signed-off-by: Nikolai Lopin <[email protected]>

docs/migrating.storybook.mdx

@@ -114,10 +114,12 @@ Consider the role the color fulfils in your use case, and pick the matching vari
 -   _shadow_.
 
 The list of semantic variables is available at [the colors page](?path=/docs/essentials-colors--docs),
-but we recommend using a typed `getSemanticValue` helper instead of hardcoding variable names (they are long).
+but we recommend using a typed `getSemanticValue` helper instead of hard-coding variable names (they are long).
 
 <CssVariablesMigrationTable />
 
+After you are done, replace all mentions of `ReadCssColorVariable | (string & {})` in your code with `ReadCssColorVariable`.
+
 ### Set the default page background to Wave's
 
 Wave has several CSS variables for page background color because of the dark/light schemes.