Add README and Godot license text

(cherry picked from commit a5ae9d9b6b)

LICENSE.txt

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+Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.
+Copyright (c) 2014-2020 Godot Engine contributors.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+## Godot Engine platform port for Haiku
+
+This is the platform port of [Godot Engine](https://godotengine.org) for the
+[Haiku](https://www.haiku-os.org) operating system.
+
+Haiku is not an officially supported platform in the main tree of Godot, so
+this port is kept separate so that it can be contributed to independently of
+Godot's main release cycle.
+
+It may imply that this port might not be functional for the latest versions of
+Godot. For the time being, neither the `3.2` branch nor the `master` branch are
+functional out-of-the-box on Haiku.
+
+We welcome all contributions from Haiku developers to ensure that each branch
+and Git tag of this repository work as expected with the matching branches and
+tags of the [Godot repository](https://github.com/godotengine/godot/).
+
+## Usage
+
+This code is meant to be copied as `platform/haiku` in the Godot Engine
+[source repository](https://github.com/godotengine/godot/) to make builds of
+Godot for Haiku.
+
+It can also be cloned as a Git submodule:
+
+```
+git clone https://github.com/godotengine/godot
+cd godot
+git submodule add https://github.com/godotengine/godot-haiku-platform platform/haiku
+```
+
+Be sure to use compatible branches for the Godot repository and the Haiku port.
+
+You can then compile Godot for Haiku with:
+
+```
+# Editor build, optimized.
+scons p=haiku tools=yes target=release_debug
+
+# Export template, debug.
+scons p=haiku tools=no target=release_debug
+# Export template, release.
+scons p=haiku tools=no target=release
+```
+
+## License
+
+This port is distributed under the MIT license, with the same copyright as the
+main Godot source repository.
+
+See [LICENSE.txt](/LICENSE.txt) for details, and
+[AUTHORS.md](https://github.com/godotengine/godot/blob/master/AUTHORS.md) in
+the Godot repository for a list of contributors.