docs: remove broken Docker TOC link and clarify Docker support in README

[victalejo]

Summary

• Removes a broken anchor link in the README table of contents that pointed to a non-existent "How to start gpt-pilot in docker?" section.
• Adds a short "Docker note" near the setup instructions clarifying that the repo ships a Dockerfile but no docker-compose.yml or dedicated Docker startup guide.

Motivation

Users clicking the Docker entry in the TOC were landing nowhere and then looking for a docker-compose.yml that does not exist in the repo. Removing the dead link and replacing it with an accurate note prevents that confusion.

Changes

• README.md: drop the 🐳 How to start gpt-pilot in docker? TOC item.
• README.md: add a ### Docker note paragraph after the workspace description pointing users to the existing Dockerfile.

Test plan

• Visually verified the TOC no longer contains the broken Docker entry.
• Visually verified the new "Docker note" section renders correctly below the setup steps.
• No code changes — documentation only.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
0 out of 5 committers have signed the CLA.

❌ Zvonimir Sabljic
❌ github-actions[bot]
❌ LeonOstrez
❌ victalejo
❌ MarkoBosnjak98

---

Zvonimir Sabljic seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}