Document Catch2's API/ABI stability policies

docs/faq.md

@@ -1,6 +1,13 @@
 <a id="top"></a>
 # Frequently Asked Questions (FAQ)
 
+**Contents**<br>
+[How do I run global setup/teardown only if tests will be run?](#how-do-i-run-global-setupteardown-only-if-tests-will-be-run)<br>
+[How do I clean up global state between running different tests?](#how-do-i-clean-up-global-state-between-running-different-tests)<br>
+[Why cannot I derive from the built-in reporters?](#why-cannot-i-derive-from-the-built-in-reporters)<br>
+[What is Catch2's ABI stability policy?](#what-is-catch2s-abi-stability-policy)<br>
+[What is Catch2's API stability policy?](#what-is-catch2s-api-stability-policy)<br>
+
 ## How do I run global setup/teardown only if tests will be run?
 
 Write a custom [event listener](event-listeners.md#top) and place the
@@ -22,6 +29,23 @@ forbidding users from using them as a base class, we can refactor them
 as needed later.
 
 
+## What is Catch2's ABI stability policy?
+
+Catch2 provides no ABI stability guarantees whatsoever. Catch2 provides
+rich C++ interface, and trying to freeze its ABI would take a lot of
+pointless work.
+
+Catch2 is not designed to be distributed as dynamic library, and you
+should really be able to compile everything with the same compiler binary.
+
+
+## What is Catch2's API stability policy?
+
+Catch2 follows [semver](https://semver.org/) to the best of our ability.
+This means that we will not knowingly make backwards-incompatible changes
+without incrementing the major version number.
+
+
 ---
 
 [Home](Readme.md#top)