port: [#6018] Move Dotnet generators from Samples to "generators" - dotnet-templates - Echo Bot (#6049)

[github-actions[bot]]

The changes in [#6018] Move Dotnet generators from Samples to "generators" - dotnet-templates - Echo Bot (#6049) may need to be ported to maintain parity with microsoft/botbuilder-dotnet.

Addresses #6018 #minor

Description

This PR adds the dotnet-templates' Echo bot from the BotBuider-Samples repository. It also includes the root documentation for the dotnet-templates folder.

Detailed Changes

• Added HOW_TO_VERSION, LICENSE, and README docs.
• Added generators/dotnet-templates/Microsoft.BotFramework.CSharp.EchoBot.
• Fixed some StyeCop issues in the code.

Testing

These images show the dotnet-template working.

Please review and, if necessary, port the changes.