SDL_shader_tools: README-SDL_gpu.md: Some updates

From 2ed9570ed4eaa5fb60c4e199e3594460d43a634e Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Fri, 13 Jan 2023 12:13:01 -0500
Subject: [PATCH] README-SDL_gpu.md: Some updates

---
 docs/README-SDL_gpu.md | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/docs/README-SDL_gpu.md b/docs/README-SDL_gpu.md
index aeb4f6d..c7ef954 100644
--- a/docs/README-SDL_gpu.md
+++ b/docs/README-SDL_gpu.md
@@ -39,10 +39,14 @@ We will _not_ support:
 - Older OpenGL and Direct3D.
 - Wild old APIs like Sony PSP/Vita homebrew, etc.
 
+## Is this going into SDL2?
+
+No, this will be part of SDL3, included in the first official release. It will not be backported to SDL2.
+
 ## What does the shader language look like?
 
 You can examine [the Shader Language Quickstart document](README-shader-language-quickstart.md), and see some
-example code at the start of the [the shader syntax megathread discussion](https://github.com/libsdl-org/SDL_shader_tools/issues/3),
+example code at the start of the [the shader syntax megathread discussion](https://github.com/libsdl-org/SDL_shader_tools/issues/3).
 
 Mostly, it looks a lot like GLSL/HLSL with some footguns removed and some
 (mostly optional!) better syntax alternatives.
@@ -131,7 +135,7 @@ If you want to do something bigger, like a corporate sponsorship,
 Longer-form writing about all of this:
 
 - [Current development branch for the API](https://github.com/icculus/SDL/tree/gpu-api)
-- [SDL_gpu.h, for API documentation](https://github.com/icculus/SDL/blob/gpu-api/include/SDL_gpu.h)
+- [SDL_gpu.h, for API documentation](https://github.com/icculus/SDL/blob/gpu-api/include/SDL3/SDL_gpu.h)
 - [SDL_shader_tools](https://github.com/libsdl-org/SDL_shader_tools), where the shader compiler is being built.
 - [Shader Language Quickstart document](README-shader-language-quickstart.md)
 - [Shader Bytecode Format document](README-bytecode-format.md)