Add README.md files for moterm and moterm_example_app.

apps/moterm/README.md

+# Moterm
+
+`moterm` is an application that provides an embeddable view, which provides a
+VT100-style terminal that its embedder can connect to other applications. It is
+not useful as a standalone application (embedded by something, like a window
+manager, that is not aware of how to control it).
+
+For an example of an embedder that's useful as a standalone application, see the
+[Moterm example application](../../examples/moterm_example_app).
+
+## Details
+
+`moterm` exposes the `mojo.terminal.Terminal` interface to its embedder. Via
+this interface, its embedder may connect to the terminal directly (for direct
+input/output with the terminal) or request that the terminal connect to another
+application. In the latter case, that application should implement the
+`mojo.terminal.TerminalClient` interface.
+
+Output to/input from the terminal is done via a `mojo.files.File` that behaves
+"like a terminal" (in much the same way as in Unix one has terminal device
+files and file descriptors to them).
+
+## See also
+
+* [//examples/moterm_example_app](../../examples/moterm_example_app)
+* [//mojo/services/files/public/interfaces](../../mojo/services/files/public/interfaces)
+* [//mojo/services/terminal/public/interfaces](../../mojo/services/terminal/public/interfaces)