[mail] Improve action documentation (#15970)

[mail] Improve action documentation (#15970)

* Use of actions.get instead of getActions

Adopt doc to newest default JS environment regarding calling mail actions via actions.get

Signed-off-by: Siegmar Immel <36704892+SiggiFR@users.noreply.github.com>
* [mail] Adding Javascript examples in documentation

Because function name has changed to get actions defined within the mail binding, the examples have been extended by a tab for JavaScript code.

* Update bundles/org.openhab.binding.mail/README.md

Co-authored-by: J-N-K <github@klug.nrw>
Signed-off-by: Siegmar Immel <36704892+SiggiFR@users.noreply.github.com>
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Signed-off-by: Siegmar Immel <36704892+SiggiFR@users.noreply.github.com>
Co-authored-by: J-N-K <github@klug.nrw>