john: add page (#3964)

pages/common/john.md

@@ -0,0 +1,36 @@
+# john
+
+> Password cracker.
+> More information: <https://www.openwall.com/john/>.
+
+- Crack password hashes:
+
+`john {{path/to/hashes.txt}}`
+
+- Show passwords cracked:
+
+`john --show {{path/to/hashes.txt}}`
+
+- Display users' cracked passwords by user identifier from multiple files:
+
+`john --show --users={{user_ids}} {{path/to/hashes*}} {{path/to/other/hashes*}}`
+
+- Crack password hashes, using a custom wordlist:
+
+`john --wordlist={{path/to/wordlist.txt}} {{path/to/hashes.txt}}`
+
+- List available hash formats:
+
+`john --list=formats`
+
+- Crack password hashes, using a specific hash format:
+
+`john --format={{md5crypt|...}} {{path/to/hashes.txt}}`
+
+- Crack password hashes, enabling word mangling rules:
+
+`john --rules {{path/to/hashes.txt}}`
+
+- Restore an interrupted cracking session from a state file, e.g. `mycrack.rec`:
+
+`john --restore={{mycrack}}`