feat: add support for Dovecot IMAP/POP3 configuration

Introduces functionality to install and configure Dovecot alongside Postfix to provide IMAP/POP3 services.

Changes include:
- Added tasks to install Dovecot packages (core, imapd, pop3d, lmtpd).
- Added templates for main configuration and conf.d files (auth, master, ssl, mail).
- Defined default variables for protocols, SSL settings, and Maildir location.
- Enabled Postfix SASL and LMTP integration options.
- Added a handler to restart the Dovecot service.
- Updated README.md with the new configuration variables and usage instructions.

handlers/main.yml

@@ -2,4 +2,9 @@
 - name: Restart Postfix
   ansible.builtin.service:
     name: postfix
+    state: restarted
+
+- name: Restart Dovecot
+  ansible.builtin.service:
+    name: dovecot
     state: restarted