feat(icons): add mailpit (#1315)

Co-authored-by: Dashboard Icons Manager <193821040+dashboard-icons-manager[bot]@users.noreply.github.com>

tree.json

@@ -1065,6 +1065,7 @@
         "mailgun.png",
         "mailhog.png",
         "mailjet.png",
+        "mailpit.png",
         "mailu.png",
         "mainsail.png",
         "maintainerr.png",
@@ -3111,6 +3112,7 @@
         "mailfence.svg",
         "mailgun.svg",
         "mailjet.svg",
+        "mailpit.svg",
         "mainsail.svg",
         "maintainerr.svg",
         "manjaro-linux.svg",
@@ -5107,6 +5109,7 @@
         "mailgun.webp",
         "mailhog.webp",
         "mailjet.webp",
+        "mailpit.webp",
         "mailu.webp",
         "mainsail.webp",
         "maintainerr.webp",