documentation: Add Pipenv support

Adds a Pipfile so that Pipenv can be used to automatically install all
the dependencies required to build the documentation

(From yocto-docs rev: 5fc0a3011c47388d9c6447c3be00fefcbaf00f5c)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 31658ad30827d38dcd4ea83bcfb828441c7c3eca)
Signed-off-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/.gitignore

@@ -1 +1,2 @@
 _build/
+Pipfile.lock

documentation/Pipfile

@@ -0,0 +1,14 @@
+[[source]]
+name = "pypi"
+url = "https://pypi.org/simple"
+verify_ssl = true
+
+[dev-packages]
+
+[packages]
+sphinx = "*"
+sphinx-rtd-theme = "*"
+pyyaml = "*"
+
+[requires]
+python_version = "3"

documentation/README

@@ -127,6 +127,13 @@ The resulting HTML index page will be _build/html/index.html, and you
 can browse your own copy of the locally generated documentation with
 your browser.
 
+Alternatively, you can use Pipenv to automatically install all required
+dependencies in a virtual environment:
+
+ $ cd documentation
+ $ pipenv install
+ $ pipenv run make html
+
 Sphinx theme and CSS customization
 ==================================