playground - templates

[RutvikGhaskataEalf]

Repo: https://github.com/AElfProject/aelf-developer-tools

If we want to add more templates, need to:

1. Develop a new template
2. Test out on local
3. Do a PR to https://github.com/AElfProject/aelf-developer-tools
4. Publish on nuget
5. Update the page at https://playground.aelf.com/ to add the new template
6. Update the page at https://playground.aelf.com/workspaces to add new template in the dropdown menu

[RutvikGhaskataEalf]

PR - AElfProject/aelf-developer-tools#54