Add input form in contribute page to contribute new template

[hemarina]

Victor and I have an offline chat on the behavior of contributing to new templates. Now, contributing guide tells customers steps to open a PR to contribute a new template. We want to change or add this workflow to an easy form in contribute page where it will ask users information and capture the inputs that require for the PR. Once user fill out the form and submit it, the back end will create a PR using pipeline/GitHub bot in awesome-azd repro, and the user gets the PR link on front end. In this way, users don't need to clone the repository if they want to contribute a new template.