release v0.5.5 (pimalaya#290)

* update main screenshot readme

* add contributing file

* update changelog

* doc: remove roadmap from reame

* improve main comments

* improve arg and handler logs

* fix multiple recipients issue (pimalaya#288)

* add notify-query config option (pimalaya#289)

* set up end-to-end encryption (pimalaya#287)

* init basic pgp encrypt/decrypt

* add small rpgp poc for (pimalaya#286)

* improve decrypt parts logs

* add pgp-decrypt-cmd to config

* add pgp-encrypt-cmd to config

* init pgp signature

* improve decrypt part readability

* improve encrypt multipart, remove sign

* remove unused md5 lib

* add encrypt arg to reply and forward commands

* fix typos

* prepare v0.5.5

release v0.5.4 (pimalaya#285)

* replace bsd3 license by bsd4

* add attachments with save and send commands (pimalaya#284)

* set up tpl save and send commands

* improve msg save and send handlers

* add vim msg#add_attachment fn

* improve vim logs

* update changelog

* add attachment keybind vim doc

* reverse range order fetch envelopes (pimalaya#276)

* bump version v0.5.4

bump version v0.5.2