update key command (#118)

Author: aawsome

src/commands/misc/key.md

@@ -1,30 +1,26 @@
 # Key - Manage repository keys
 
-**⚠️ Be aware**: This is not yet implemented!
-
 The `key` command allows you to set multiple access keys or passwords per
 repository. In fact, you can use the `list`, `add`, `remove`, and `passwd`
 (changes a password) sub-commands to manage these keys very precisely:
 
 ```console
     $ rustic key list
     enter password for repository:
-     ID          User        Host        Created
-    ----------------------------------------------------------------------
-    *eb78040b    username    kasimir   2015-08-12 13:29:57
+    | ID        | User     | Host    | Created                              |
+    |-----------|----------|---------|--------------------------------------|
+    | *8a9d4286 | username | kasimir | 2025-08-12 13:29:57.759858440 +02:00 |
 
-    $ rustic key add
-    enter password for repository:
-    enter password for new key:
-    enter password again:
-    saved new key as <Key of username@kasimir, created on 2015-08-12 13:35:05.316831933 +0200 CEST>
+    $ rustic key add --with-created --username alex --hostname batman
+    enter password for new key: [hidden]
+    [INFO] key 70970299 successfully added.
 
     $ rustic key list
     enter password for repository:
-     ID          User        Host        Created
-    ----------------------------------------------------------------------
-     5c657874    username    kasimir   2015-08-12 13:35:05
-    *eb78040b    username    kasimir   2015-08-12 13:29:57
+    | ID        | User     | Host    | Created                              |
+    |-----------|----------|---------|--------------------------------------|
+    | *8a9d4286 | username | kasimir | 2025-08-12 13:29:57.759858440 +02:00 |
+    | 70970299  | alex     | batman  | 2025-10-11 22:37:29.759858440 +02:00 |
 ```
 
 **Note**: that the currently used key is indicated by an asterisk (`*`).