Add build guide to README

Signed-off-by: Michal Konecny <mkonecny@redhat.com>

.gitignore

@@ -0,0 +1 @@
+.venv/

README.md

@@ -5,3 +5,33 @@ the investigation that the ARC team leads.
 
 More documentation about the team can be found at:
 https://fedora-arc.readthedocs.io/en/latest/index.html
+
+
+## How to build locally
+
+1. Create python virtual environment
+
+   ```
+   python3 -m venv .venv
+   ```
+
+2. Activate virtual environment
+
+   ```
+   . .venv/bin/activate
+   ```
+
+3. Install requirements
+
+   ```
+   pip install -r docs/requirements.txt
+   ```
+
+4. Execute the Makefile
+
+   ```
+   cd docs
+   make html
+   ```
+
+5. You will find the compiled HTML in `docs/_build/html`

docs/requirements.txt

@@ -1,2 +1,3 @@
 myst_parser
+sphinx
 sphinx-rtd-theme