https://addons.mozilla.org/firefox/language-tools/ is where we list the dictionaries. I haven’t heard of helpers for the packaging, but you shouldn’t need much more than a zip. Download one of the currently maintained ones there to see the structure.
We also ship hunspell dictionaries as part of our localized builds, but to include this with the Persian localization, we’d need it to be under a license that’s compatible with MPL 2. https://wiki.mozilla.org/L10n:Dictionaries has details on that. Feel free to list your dictionary there either way, though.