Har importer package #122

[ayaan-md-blr]

PR Description

1. Created a new package har_parser to implement the import of api collections from har file.
2. Contains only the backend. UI integration will follow post review and approval of this PR

Related Issues

• Closes Importing Requests from HAR file #122

Checklist

• I have gone through the contributing guide
• I have updated my branch and synced it with project main branch before making this PR
• I am using the latest Flutter stable branch (run flutter upgrade and verify)
• I have run the tests (flutter test) and all tests are passing

Added/updated tests?

_ har_parser/test

• Yes

OS on which you have developed and tested the feature?

• Windows
• macOS

[ashitaprasad]

This PR is incomplete.
Take a deeper look at the code base and understand how other importers like Insomnia & Postman are implemented.