Created main.yml file to setup GitHub Action

[saamerm]

• Added main.yml file that orders 2 jobs on every push and merge request
• One job is to build iOS and the other builds Android

Purpose of Action

• The action performs a sanity test on your apps— makes sure the iOS & Android apps build on each commit or merge request, ensuring that there is no bug introduced in that commit
• More details in the article or the corresponding unmetered article link

Testing

• Tested the Action on my fork and it passed the tests