Project page to describe AWS related things of Application in Console

**Is your feature request related to a problem? Please describe.**
As a developer, I want my new team member to learn our project detail around AWS easily so that I don't need to provide the same explanation for many times.

**Describe the solution you'd like**
Specify a `.md` file and host as project detail in Application page of Console. The other way would be putting a textarea and users fill.

**Additional context**
Currently, developers have their own README per application. For backend related resource, some of them may want to take out from README and have a separeted description file. If Amplify can recorgnize the description file and host it on their console, then new team member can be easiley on boarded a bit more.

Review the existing per-application README files and the Application page in Console to understand how project details are currently presented. Define whether the work should use a separate .md file or a textarea, and consider the work complete when AWS-related application details are hosted in Console for new team members to read.

Written by the indexing model from the issue text.