docs: Add FAQ section

Change-Id: Ia45a4ec0dcae0279b6ebc9bc542377f154f7a0b2
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/14780
Reviewed-by: David Rogers <davidrogers@google.com>
Commit-Queue: Keir Mierle <keir@google.com>
diff --git a/docs/index.rst b/docs/index.rst
index d7eff04..a7230ed 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -21,5 +21,6 @@
   Code Style <docs/style_guide>
   targets
   Build System <build_system>
+  FAQ <docs/faq>
   docs/module_structure
   module_guides