Adding template project and correct name

vendor/rmlui_backend/RmlUi_SDL_GPU/SDL_shadercross/LICENSE.txt

@@ -0,0 +1,28 @@
+The SDL GPU backend for RmlUi uses the following third-party tool to generate
+the included shader binaries:
+
+SDL_shadercross
+https://github.com/libsdl-org/SDL_shadercross
+
+This tool is licensed separately from Rmlui. The license of this dependency
+is recited below.
+
+----
+
+Copyright (C) 2024 Sam Lantinga <slouken@libsdl.org>
+
+This software is provided 'as-is', without any express or implied
+warranty.  In no event will the authors be held liable for any damages
+arising from the use of this software.
+
+Permission is granted to anyone to use this software for any purpose,
+including commercial applications, and to alter it and redistribute it
+freely, subject to the following restrictions:
+
+1. The origin of this software must not be misrepresented; you must not
+   claim that you wrote the original software. If you use this software
+   in a product, an acknowledgment in the product documentation would be
+   appreciated but is not required.
+2. Altered source versions must be plainly marked as such, and must not be
+   misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.