Add README.md (WIP)

README.md

+# (*Working Title*) Typon
+
+> typon \ti.pɔ̃\ masculin
+>
+> (Imprimerie) Masque, feuille transparente, sur laquelle est imprimé un motif
+> dans une encre opaque qui permet d'insoler, puis de graver la plaque qui
+> servira à imprimer.
+>
+> (Électronique) Masque transparent sur lequel sont imprimées les pistes, dans
+> une encre opaque aux ultraviolets, permettant de réaliser un circuit imprimé
+> par photogravure soustractive.
+
+
+Typon is a three-part project to bring practical GIL-free concurrency to Python:
+1. [ ] Write a C++ concurrency runtime
+2. [ ] Write a compiler from Python syntax into C++
+3. [ ] Add C++/Python bindings for interoperability with actual Python
+
+Step 1 is currently in progress.
+
+
+## (*in progress*) `typon/rt`, A Concurrency Runtime
+
+A continuation-stealing concurrency runtime using cutting-edge C++20 coroutines,
+featuring both `fork`/`sync` structured concurrency and `future`-based unbounded
+concurrency.
+
+### Status
+
+- [x] structured concurrency with `fork`/`sync`
+- [x] systematic exception propagation from `fork`ed tasks
+- [x] unbounded concurrency with `future`
+- [x] asynchronous waiting (`Promise`, `future`/`Future`)
+- [ ]  channels (single producer, single consumer)
+- [ ]  mutexes (with asynchronous blocking)
+- [ ]  asynchronous I/O
+- [ ]  builtin task cancellation
+
+
+### `fork`/`sync`, Structured Concurrency
+
+```C++
+using namespace typon;
+
+Join<int> fibo(int n) {
+  if (n < 2) {
+    co_return n;
+  }
+  // Start two potentially concurrent tasks
+  Forked a = co_await fork(fibo(n - 1));
+  Forked b = co_await fork(fibo(n - 2));
+  // Wait until they both complete
+  co_await Sync();
+  // Access the results
+  co_return a.get() + b.get();
+}
+```
+
+
+### `future`, Unbounded Concurrency
+
+```
+using namespace typon;
+
+Task<int> fibo(int n) {
+  if (n < 2) {
+    co_return n;
+  }
+  // Start two potentially concurrent tasks
+  Future a = co_await future(fibo(n - 1));
+  Future b = co_await future(fibo(n - 2));
+  // Wait for each future and retrieve the results
+  co_return co_await a.get() + co_await b.get();
+}
+```
+
+### References
+
+- https://en.wikipedia.org/wiki/Work_stealing#Child_stealing_vs._continuation_stealing
+
+- https://en.wikipedia.org/wiki/Futures_and_promises
+