Add steps, How to run and deploy the project

[hashirshoaeb]

Is your feature request related to a problem? Please describe.
Readme should have steps on how to run the project locally on machine. Preferably, also how to deploy it.

Describe the solution you'd like

Run on staging debug:

• flutter run --dart-define=flavor=qa

Run on production:

• flutter run --dart-define-from-file=.env.prod.json

Deploy to iOS:

• flutter build ipa --release --dart-define-from-file=.env.prod.json

Deploy to Android:

• flutter build appbundle --release --dart-define-from-file=.env.prod.json

where .env.prod.json is the file containing the production environment variables.

{
  "flavor": "prod",
  "apiKey": "<FIREBASE_API_KEY>",
  "appIdAndroid": "<FIREBASE_APP_ID>",
  "appIdIos": "<FIREBASE_APP_ID>",
  "messagingSenderId": "<FIREBASE_MESSAGING_SENDER_ID>",
  "projectId": "<FIREBASE_PROJECT_ID>",
  "storageBucket": "<FIREBASE_STORAGE_BUCKET>",
  "iosBundleId": "<IOS_BUNDLE_ID>",
}