doc: provide the python engine in a virtualenv

* Documents how to use `pyenv` to provide a virtual environment for the
  python engine.

Co-Authored-by: iGor milhit <igor@milhit.ch>

README.md

@@ -10,7 +10,7 @@ I'm using the [nord color scheme][5].
 
 ## To do
 
-- [ ] Document how to use `pyenv` to provide a python engine.
+- [x] Document how to use `pyenv` to provide a python engine.
 - [ ] Identify the python package dependencies.
   - `jedi`.
   - `jedi-language-server`.
@@ -63,6 +63,50 @@ export FZF_DEFAULT_OPTS="--preview='bat --style=numbers --color=always --line-ra
 
 See the `fzf` documentation: <https://github.com/junegunn/fzf#preview-window>
 
+## Provide an virtual environment for python engine
+
+Benefit: having a separate virtual environment for your editor than the one
+your working into.
+
+Install `pyenv` with the [`pyenv-installer`][9].
+
+Install the python version you need with `pyenv`:
+
+```bash
+pyenv install 3.9.9
+```
+
+Create and name the virtual environment for neovim:
+
+```bash
+pyenv virtualenv 3.9.9 neovim
+```
+
+Activate the virtual environment and fetch the python path:
+
+```bash
+pyenv activate neovim
+pyenv which python      #Note the provided path
+```
+
+Add the following line to your `init.vim`:
+
+```init.vim
+let g:python3_host_prog = '/full/path/to/neovim/bin/python
+```
+
+Install the python dependencies in the virtual environment as it is activated:
+
+```bash
+pip install neovim pynvim …
+```
+
+To deactivate the virtual environment:
+
+```bash
+pyenv deactivate
+```
+
 [1]: https://github.com/junegunn/vim-plug
 [2]: https://github.com/BurntSushi/ripgrep
 [3]: https://github.com/ggreer/the_silver_searcher
@@ -70,3 +114,4 @@ See the `fzf` documentation: <https://github.com/junegunn/fzf#preview-window>
 [5]: https://www.nordtheme.com/ports/vim
 [7]: https://github.com/junegunn/vim-plug#installation
 [8]: https://www.gitmemory.com/ryanoasis/nerd-fonts
+[9]: https://github.com/pyenv/pyenv-installer