Update README, and translate to Markdown

Author: pradyunsg

README.md

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+# get-pip.py
+
+`get-pip.py` is a bootstrapping script that enables users to install pip,
+setuptools, and wheel in Python environments that don't already have them. You
+should not directly reference the files located in this repository and instead
+use the versions located at <https://bootstrap.pypa.io/>.
+
+## Usage
+
+```console
+$ curl -sSL https://bootstrap.pypa.io/get-pip.py -o get-pip.py
+$ python get-pip.py
+```
+
+Upon execution, `get-pip.py` will install `pip`, `setuptools` and `wheel` in
+the current Python environment.
+
+It is possible to provide additional arguments to the underlying script. These
+are passed through to the underlying `pip install` command, and can thus be
+used to constraint the versions of the packages, or to pass other pip options
+such as `--no-index`.
+
+```console
+$ python get-pip.py "pip < 21.0" "setuptools < 50.0" "wheel < 1.0"
+$ python get-pip.py --no-index --find-links=/local/copies
+```
+
+### get-pip.py options
+
+This script also has it's own options, which control which packages it will
+install.
+
+- `--no-setuptools`: do not attempt to install `setuptools`.
+- `--no-wheel`: do not attempt to install `wheel`.
+
+## Development
+
+You need to have a [`nox`](https://nox.readthedocs.io/) available on the CLI.
+
+### How it works
+
+`get-pip.py` bundles a copy of pip with a tiny amount of glue code. This glue
+code comes from the `templates/` directory.
+
+### Updating after a pip release
+
+If you just made a pip release, run `nox -s update-for-release -- <version>`.
+This session will handle all the script updates (by running `generate`), commit
+the changes and tag the commit.
+
+IMPORTANT: Check that the correct files got modified before pushing. The session
+will pause to let you do this.
+
+### Generating the scripts
+
+Run `nox -s generate`.
+
+## Discussion
+
+If you run into bugs, you can file them in our [issue tracker].
+
+You can also join `#pypa` or `#pypa-dev` on Freenode to ask questions or
+get involved.
+
+[issue tracker]: https://github.com/pypa/get-pip/issues
+
+## Code of Conduct
+
+Everyone interacting in the get-pip project's codebases, issue trackers, chat
+rooms, and mailing lists is expected to follow the [PSF Code of Conduct].
+
+[PSF Code of Conduct]: https://github.com/pypa/.github/blob/main/CODE_OF_CONDUCT.md