tlmgr-key: add page (#8193)

pages/common/tlmgr-key.md

@@ -0,0 +1,20 @@
+# tlmgr key
+
+> Manage GPG keys used to verify TeX Live databases.
+> More information: <https://www.tug.org/texlive/tlmgr.html>.
+
+- List all keys for TeX Live:
+
+`tlmgr key list`
+
+- Add a key from a specific file:
+
+`sudo tlmgr key add {{path/to/key.gpg}}`
+
+- Add a key from stdin:
+
+`cat {{path/to/key.gpg}} | sudo tlmgr key add -`
+
+- Remove a specific key by its ID:
+
+`sudo tlmgr key remove {{key_id}}`