Add cURL cheatsheet and GPG key renewing

how_to

@@ -1036,3 +1036,25 @@ Consistent desktop theme:
     themes:
         Gruvbox-Material-Dark has issues with GIMP and probably caused a few other crashes
         gruvbox-dark-[icons-]gtk doesn't look too bad at first glance (GIMP not broken) (is on AUR)
+
+cURL cheatsheet:
+    custom user agent:
+        curl -A "<user agent>" <URL>
+    Show headers:
+        Just response headers
+            curl -I <URL>
+        full verbose dump
+            curl -v <URL>
+    Follow redirects:
+        curl -L <URL>
+
+GPG:
+    Renew expired GPG public keys:
+        # https://unix.stackexchange.com/a/177310/248368
+        gpg --edit-key "<key>"
+        > expire
+        ...
+        > key 1
+        > expire
+        ...
+        > save