doc dev/pyenv improve layout

hugo/content/dev/pyenv.md

@@ -3,15 +3,18 @@ title = "Pyenv"
 weight = 80
 +++
 
+
+## pyenv
+
 [Pyenv](https://github.com/pyenv/pyenv) is a platform to install and manage
 different versions of Python, isolated from the default Python version.
 Its advantage compared to the other options, like Anaconda, is its simplicity and smallness.
 Currently, to build BornAgain libraries for different versions of Python,
 we use the `pyenv` platform.
 
-# Installing `pyenv` platform
+#### Installation
 
-#### Linux
+##### Linux
 
 Obtain the installer from <https://github.com/pyenv/pyenv-installer>.
 To install `pyenv`, use
@@ -29,7 +32,7 @@ libbz2-dev libreadline-dev libsqlite3-dev curl \
 libncursesw5-dev xz-utils tk-dev libxml2-dev libxmlsec1-dev libffi-dev liblzma-dev
 ```
 
-#### MacOS
+##### MacOS
 
 Install `pyenv` via `homebrew`:
 ```
@@ -39,7 +42,7 @@ brew install pyenv
 The rest of the `pyenv` instructions are like those for Linux.
 
 
-#### Windows
+##### Windows
 
 On MS-Windows, [pyenv-win](https://github.com/pyenv-win) should be used.
 
@@ -54,7 +57,7 @@ echo %PYENV_ROOT%
 ```
 
 
-#### Using `pyenv`
+#### Using pyenv
 
 **Obtain a list of available Python versions**
 ```