sdl12-compat: HOW_TO_TEST_GAMES: Note Steam Runtime has SDL2.

From f689f8bcbf49f2be3e43dde2c54c865ffda6d326 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Fri, 2 Sep 2022 16:14:51 -0400
Subject: [PATCH] HOW_TO_TEST_GAMES: Note Steam Runtime has SDL2.

---
 HOW_TO_TEST_GAMES.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/HOW_TO_TEST_GAMES.md b/HOW_TO_TEST_GAMES.md
index a32a4343..74c64b45 100644
--- a/HOW_TO_TEST_GAMES.md
+++ b/HOW_TO_TEST_GAMES.md
@@ -82,6 +82,9 @@ If testing a Steam game, you'll want to launch the game outside of the Steam
 Client, so that Steam doesn't overwrite files you replaced and so you can
 easily control environment variables.
 
+Since you'll be using the Steam Runtime, you don't have to find your own copy
+of SDL2, as Steam provides it.
+
 On Linux, Steam stores games in ~/.local/share/Steam/steamapps/common, each
 in its own usually-well-named subdirectory.