Better support GPG migrations

After yet another unpleasant experience starting up GPG on a new system, I
decided to encode my learnings and mistakes as aliases, functions, scripts,
hoping to protect my future me from myself. Fingers crossed!

configs/shared/gpg/.gnupg/import.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+set -e
+
+# Run this script to import all of the information exported by `export.sh`.
+# Usage: ./export.sh path/to/directory
+
+gpg --import "$1/public.asc"
+gpg --import "$1/secret.asc"
+gpg --import-ownertrust "$1/ownertrust.txt"
+
+# Run this at the end to output some verification
+gpg --list-keys