Add README for examples (#489)
Add README for examples (#489)

* Add README for examples

* Fix typo in examples/README.md

Co-authored-by: Paolo Barbolini <f5973ee9c413d0967b98e0944688acb235fd48bf@paolo565.org>

* Update examples/README.md

Add links to source files and improve wording.

* Fix typos in examples/README.md

* Update examples/README.md

Fix typo.
Add line under title.

Co-authored-by: Paolo Barbolini <f5973ee9c413d0967b98e0944688acb235fd48bf@paolo565.org>

* Fix typo in examples/README.md

Co-authored-by: Paolo Barbolini <f5973ee9c413d0967b98e0944688acb235fd48bf@paolo565.org>
amousset/rust-smtp,amousset/lettre,lettre/lettre,amousset/lettre