Add tomlgen_rust to README commands with a link to example

Author: Martin Larralde

README.rst

@@ -128,3 +128,7 @@ Commands
 * `clean` - Standard `clean` command executes `cargo clean` for all rust extensions.
 
 * `check` - Standard `check` command executes `cargo check` for all rust extensions.
+
+* `tomlgen_rust` - Automatically generate a `Cargo.toml` manifest based on Python package metadata.
+  See the `example project <https://github.com/PyO3/setuptools-rust/tree/master/example_tomlgen>`_
+  on GitHub for more information about this command.

example_tomlgen/README.rst

@@ -1,7 +1,7 @@
 `example_tomlgen`
 =================
 
-An example extensions with automatically generated ``Cargo.toml`` manifest
+An example extension with automatically generated ``Cargo.toml`` manifest
 files. Simply run ``python setup.py tomlgen_rust`` to generate the following
 files:
 
@@ -80,7 +80,7 @@ project (next to the ``setup.py`` file) which registers all of the extensions.
 This way, generic ``cargo`` commands can be run without leaving the root of
 the project.
 
-If ``--create-workspace`` is enable, a `.cargo/config` file will also be
+If ``--create-workspace`` is enabled, a `.cargo/config` file will also be
 created to force ``cargo`` to build to the temporary build directory. Use
 ``--no-config`` to disable.