* Update configuring-playbook.md: move a link for docs/configuring-playbook-bot-postmoogle.md to Bots section

The document (on 9c2a8addee93910cb9079f856bc3fb3932592c91; initial commit to add Postmoogle) says:
> Postmoogle is a bot/bridge you can use to forward emails to Matrix rooms

Therefore it is not really incorrect to categorize Postmoogle as bridge document-wise, but since the list on README.md categorizes it as a bot, and based on the file name of the documentation, this commit moves the link for Postmoogle to the Bots section.

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Revert "Update configuring-playbook.md: move a link for docs/configuring-playbook-bot-postmoogle.md to Bots section"

This reverts commit 1e2e903cb9.

* Change the file name of Postmoogle documentation to make it clear that Postmoogle is a bridge

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Update documentation for Postmoogle related to a bridge/bot status

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

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Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>
Co-authored-by: Suguru Hirahara <acioustick@noreply.codeberg.org>