Move or remove some redundant information from the README

* Move the folder structure to ARCHITECTURE.md (which can be
  expanded as per #707)

* Move the acknowledgements to CONTRIBUTORS.md

* Remove the history (it's a copy of man/rgbds.7)

ARCHITECTURE.md

@@ -0,0 +1,69 @@
+# RGBDS Architecture
+
+## Folder Organization
+
+The RGBDS source code file structure is as follows:
+
+```
+.
+├── .github/
+│   ├── scripts/
+│   │   └── ...
+│   └── workflows/
+│       └── ...
+├── contrib/
+│   ├── zsh_compl/
+│   │   └── ...
+│   └── ...
+├── include/
+│   └── ...
+├── man/
+│   └── ...
+├── src/
+│   ├── asm/
+│   │   └── ...
+│   ├── extern/
+│   │   └── ...
+│   ├── fix/
+│   │   └── ...
+│   ├── gfx/
+│   │   └── ...
+│   ├── link/
+│   │   └── ...
+│   ├── CMakeLists.txt
+│   └── ...
+├── test/
+│   ├── ...
+│   └── run-tests.sh
+├── .clang-format
+├── CMakeLists.txt
+├── compile_flags.txt
+├── Dockerfile
+└── Makefile
+```
+
+- `.github/` - files and scripts related to the integration of the RGBDS codebase with
+  GitHub.
+  * `scripts/` - scripts used by workflow files.
+  * `workflows/` - CI workflow description files.
+- `contrib/` - scripts and other resources which may be useful to users and developers of
+  RGBDS.
+  * `zsh_compl` - contains tab completion scripts for use with zsh. Put them somewhere in
+    your `fpath`, and they should auto-load.
+  * `bash_compl` - contains tab completion scripts for use with bash. Run them with `source`
+    somewhere in your `.bashrc`, and they should load every time you open a shell.
+- `include/` - header files for the respective source files in `src`.
+- `man/` - manual pages.
+- `src/` - source code of RGBDS.
+  * Note that the code unique to each RGBDS tool is stored in its respective subdirectory
+    (RGBASM's code is in `src/asm/`, for example). `src/extern/` contains code imported from
+    external sources.
+- `test/` - testing framework used to verify that changes to the code don't break or
+  modify the behavior of RGBDS.
+- `.clang-format` - code style for automated C++ formatting with
+  [`clang-format`](https://clang.llvm.org/docs/ClangFormat.html).
+- `CMakeLists.txt` - defines how to build RGBDS with CMake.
+- `compile_flags.txt` - compiler flags for C++ static analysis with
+  [`clang-tidy`](https://clang.llvm.org/extra/clang-tidy/).
+- `Dockerfile` - defines how to build RGBDS with Docker.
+- `Makefile` - defines how to build RGBDS with `make`.