Add how-to for replyng to comments

[mikeebowen]

This is in response to this issue on the OOXML SDK

[learn-build-service-prod]

Learn Build status updates of commit 99cb04c:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/presentation/how-to-reply-to-a-comment-in-a-presentation.md	✅Succeeded
docs/presentation/overview.md	✅Succeeded
docs/toc.yml	✅Succeeded
samples/presentation/create_by_providing_a_file_name/cs/Program.cs	✅Succeeded
samples/presentation/reply_to_comment/cs/Program.cs	✅Succeeded
samples/presentation/reply_to_comment/cs/reply_to_comment_cs.csproj	✅Succeeded
samples/presentation/reply_to_comment/vb/Program.vb	✅Succeeded
samples/presentation/reply_to_comment/vb/reply_to_comment_vb.vbproj	✅Succeeded
samples/samples.sln	✅Succeeded

For more details, please refer to the build report.

[learn-build-service-prod]

Learn Build status updates of commit 81386b3:

✅ Validation status: passed

File	Status	Preview URL	Details
.gitattributes	✅Succeeded
docs/presentation/how-to-reply-to-a-comment-in-a-presentation.md	✅Succeeded
docs/presentation/overview.md	✅Succeeded
docs/toc.yml	✅Succeeded
samples/presentation/create_by_providing_a_file_name/cs/Program.cs	✅Succeeded
samples/presentation/reply_to_comment/cs/Program.cs	✅Succeeded
samples/presentation/reply_to_comment/cs/reply_to_comment_cs.csproj	✅Succeeded
samples/presentation/reply_to_comment/vb/Program.vb	✅Succeeded
samples/presentation/reply_to_comment/vb/reply_to_comment_vb.vbproj	✅Succeeded
samples/samples.sln	✅Succeeded

For more details, please refer to the build report.