docs: add installation section

docs/source/index.rst

@@ -11,6 +11,7 @@ Welcome to checkcert's documentation!
    :caption: Contents:
 
    introduction
+   install
 
 
 

docs/source/install.rst

@@ -0,0 +1,26 @@
+Installation
+============
+
+From Pypi
+---------
+
+The easiest way is to install via pypi via:
+
+``pip install checkcert``
+
+If you already have checkcert installed and wish to update it, run:
+
+``pip install -U checkcert``
+
+This will upgrade the currently-installed version to the latest.
+
+From Git
+--------
+
+There are many methods for running within a virtual environment isolated for a particular package.  Certcheck has been built with poetry, so this document details that method, but there are certainly other ways to accomplish the same thing
+
+1. clone the repo ``git clone https://github.com/kellya/checkcert.git``
+2. cd to the directory you just cloned ``cd checkcert``
+3. install the required packages ``poetry install``
+4. activate the poetry-built venv ``poetry shell``
+5. run with ``python certcheck/certcheck.py``