README update: Include Arduino IDE 2 information.

[VarshiniShreeV]

Description

This pull request adds references to Arduino IDE 2 in the README file and the issue template. This aims to help users who are less familiar with Arduino to direct them to the new IDE, reducing confusion regarding the old repository.

Related Issues

Resolves: arduino#11977, arduino#11980

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

New Feature Submissions:

1. Does your submission pass tests?
2. Have you linted your code locally prior to submission?

Changes to Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully run tests with your changes?

[VarshiniShreeV]

This pull request updates the README and the issue template to include references to Arduino IDE 2. This change aims to guide users who may be less familiar with the Arduino platform to the current IDE, reducing confusion about the status of the old repository. It resolves issues arduino#11977 and arduino#11980.