docc: readme.md

### Describe your issue

Readme should mention the supported versions of task warrior. 2, 3, or both

### Steps to reproduce

No steps as this is a document update

### What was the expected result?

No result other than correct decision making

### Put here any screenshots or videos (optional)

_No response_

### How can we contact you (optional)

_No response_

### Would you like to work on this issue?

None

### By submitting this issue, I have confirmed that:

- [x] I have starred the repo ⭐ and watched 👀 it on GitHub and followed the contribution guidelines.