Add CODEOWNERS entry for copilot-instructions.md (Azure#43856)

Author: maririos

.github/CODEOWNERS

@@ -840,6 +840,7 @@
 /eng/common/                                                         @Azure/azure-sdk-eng
 /.github/workflows/                                                  @Azure/azure-sdk-eng
 /.github/CODEOWNERS                                                  @lmazuel @xiangyan99 @kashifkhan @Azure/azure-sdk-eng
+/.github/copilot-instructions.md                                     @l0lawrence @praveenkuttappan @maririos
 /sdk/pullrequest.yml                                                 @scbedd @weshaggard @benbp
 
 /.config/1espt/                                                      @benbp @weshaggard