Initial Sphinx-based documentation templates and infra

Change-Id: I180ad109b8a885df6fd8911729289cee5c9bd99f
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..1b6ba26
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+doc_venv
+_build