update the readme on how to build the docs

README.md

@@ -305,8 +305,32 @@ and when I want to test some commands against such config file I just source it:
     source .env
     cargo run -- in 'hola'
 
+### Documentation
+
+The docs are written using [sphinx](https://www.sphinx-doc.org/en/master/), so
+first you need to install it somehow. Two options I can offer are:
+
+* using your computer's package manager. Install a package with a name similar
+  to `python-sphinx`.
+* using [pipenv](https://duckduckgo.com/?t=ffab&q=pipenv&ia=web). Just ensure
+  you have python 3.9 on your computer, enter the `docs` directory and do
+  `pipenv install`.
+
+To build the docs just enter the `docs` directory and some of the language
+directories (currently `es` or `en`) and run:
+
+    make html
+
+for the html version (output located at `docs/<lang>/build/html`), or
+
+    make man
+
+for the man page (output located at `docs/<lang>/build/man/tiempo.1`). If you
+are using pipenv just prefix the commands with `pipenv run` or run `pipenv
+shell` before running any command.
+
 ## Special Thanks
 
-To [timetrap](https://github.com/samg/timetrap) for existing. It is the tool I
-was looking for and whose design I took as reference, keeping compatibility when
-possible.
+To [timetrap](https://github.com/samg/timetrap) for existing, to
+[samg](https://github.com/samg) for creating it. It is the tool I was looking
+for and whose design I took as reference, keeping compatibility when possible.