doc: update readme toc #no_auto_pr
- [Installing sbp2json, json2sbp, json2json and related tools](#installing-sbp2json-json2sbp-json2json-and-related-tools)
- [Building / installing](#building--installing)
* [Using Docker](#using-docker)
+ + [Using the prebuilt image from DockerHub](#using-the-prebuilt-image-from-dockerhub)
+ [Creating your own image](#creating-your-own-image)
- + [Using the prebuilt one from dockerhub](#using-the-prebuilt-one-from-dockerhub)
+ + [Using the docker image](#using-the-docker-image)
* [Installing from package managers](#installing-from-package-managers)
* [Installing development Python versions](#installing-development-python-versions)
* [Adding development version as a pip dependency](#adding-development-version-as-a-pip-dependency)
