Add local development environment setup instructions

[mahmoudnasser1561]

Provide a general description of the issue or problem.

Problem

Dev environment setup steps are not easy to discover from the repository root.
As a new contributor, I had to hunt across docs to find the right instructions.

Proposal

Add a short, repo-local development setup guide (conda + venv/pip), and link it
from README and the docs index.

Scope

Docs-only. No behavior changes.

What I plan to include

• conda setup (Python 3.12)
• venv/pip setup
• (optional) docs build command if supported

If this sounds good, I’ll open a PR referencing this issue.

[samaloney]

The overall idea sounds good but we should post to and use as much of sunpy's dev documentation as we can an only hight the specifics differences

[dhanushsaimudari]

Hi @samaloney ! I have created PR request on the #149 issue about "'setup instructions for a local development", and I have changed in only readme file, and didn't changed any other document because most of the contributor mainly focuses on readme than other docs for setting up first time.

IF it's perfect then would like to add in other docs files