Fix environment variable not found for authKey

[vishwamartur]

Related to #1

Update the environment variable for authKey and add documentation for setting up the .env file.

• lib/env/env.dart

  • Update the @EnviedField annotation to use varName: 'AUTH_KEY' instead of varName: 'AUTH-KEY'.

• .gitignore

  • Remove the .env entry from the ignore list.

• .env

  • Add a new .env file with the content AUTH_KEY=your_auth_key_here.

• README.md

  • Add a section to document the need for a .env file and the required AUTH_KEY variable.
  • Include instructions for running the project after setting up the .env file.

[mrcodefrost]

Hi @vishwamartur , this is working thanks, i was able to generate the .env.g.dart but

1. Where can i get the auth key ? @vishwamartur @harsimran-d

Note : In case same error is popping up after this change then refer to below solution

2. Issue : Flutter was unable to detect the .env in root folder. ( root file is the one where your pubspec.yaml resides in hierarchy)
   Solution :
   I refactored it to secrets.env,
   ran the build_runner, it then ran successfully.
   Refactored it back to .env and deleted old g files and ran the build_runner again.

Worked perfectly this way