Add Python installation to chrome/desarrolladores/biseccion.md

- Add steps on how to install Python in several OSs.
- Update step to download the bisect tool in Windows (it is now using
  PowerShell syntax and Python 3 instead of Python 2).
- Minor improvements to the guide.
- Add pymdownx.keys and pymdownx.details MD extensions.

Change-Id: I51e3fd78d8c9acfe3cac9cdf40fe531900ffdaa3
diff --git a/mkdocs.yml b/mkdocs.yml
index 313af5f..5abce73 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -21,6 +21,8 @@
       permalink: true
   - pymdownx.tabbed
   - pymdownx.superfences
+  - pymdownx.keys
+  - pymdownx.details
 nav:
   - 'Sobre esta web': 'index.md'
   - 'Chrome':