The playbook tags are not limited to installation, and the explanation's detail makes the section worth being split to a dedicated individual page.

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

Since we'll likely have generic SQLite database importing
via [pgloader](https://pgloader.io/) for migrating bridge
databases from SQLite to Postgres, we'd rather avoid
calling the "import Synapse SQLite database" command
as just `--tags=import-sqlite-db`.

Similarly, for the media store, we'd like to mention that it's
related to Synapse as well.

We'd like to be more explicit, so as to be less confusing,
especially in light of other homeserver implementations
coming in the future.

Related to #583 (Github Issue).