[#9] Set up project app flavors

[lydiasama]

• Close #9

What happened 👀

• Added Production and Staging app flavors
• Added release and debug build type
• Generated keystone for both release and debug
• Configured app name for staging and production flavor

Insight 📝

The release.keystore and signing.properties are provided in 1P here.

Proof Of Work 📹

[luongvo]

This PR should be based on https://github.com/nimblehq/kmm-templates/pull/28 to verify the generated project changes.

[phongvhd93]

@lydiasama please resolve the conflict

[lydiasama]

@phongvhd93 Done. 🙏🏻