Exclude link from link checking

Used as an example for Copilot, so doesn't need to be a working link.

Author: martincostello

.github/copilot-instructions.md

@@ -510,6 +510,7 @@ Use the following values for option:
 Use a short sentence for the summary.
 After the summary sentence and in the same cell,
 link to further details using the following format,
+<!-- markdown-link-check-disable-next-line -->
 "Refer to [option](#option-anchor) for details."
 
 In the values column, describe acceptable values