Update READMEs per tinywl merge

rootston/README.md

@@ -0,0 +1,18 @@
+# rootston
+
+Rootston is the "big" wlroots test compositor. It implements basically every
+feature of wlroots and may be useful as a reference for new compositors.
+However, it's mostly used as a testbed for wlroots development and does not have
+particularly clean code and is not particularly well designed: proceed with a
+grain of salt. It is not designed for end-users.
+
+## Running rootston
+
+If you followed the build instructions in `../README.md`, the rootston
+executable can be found at `build/rootston/rootston`. To use it, refer to the
+example config at [rootston/rootston.ini.example][rootston.ini] and place a
+config file of your own at `rootston.ini` in the working directory (or in an
+arbitrary location via `rootston -C`). Other options are available, refer to
+`rootston -h`.
+
+[rootston.ini]: https://github.com/swaywm/wlroots/blob/master/rootston/rootston.ini.example