7z: add encrypted (including headers) archive (#1918)

pages/common/7z.md

@@ -6,17 +6,21 @@
 
 `7z a {{archived.7z}} {{path/to/file}}`
 
+- Encrypt an existing archive (including headers):
+
+`7z a {{encrypted.7z}} -p{{password}} -mhe {{archived.7z}}`
+
 - Extract an existing 7z file with original directory structure:
 
-`7z x {{archived}}`
+`7z x {{archived.7z}}`
 
 - Extract an archive with user-defined output path:
 
-`7z x {{archived}} -o{{path/to/output}}`
+`7z x {{archived.7z}} -o{{path/to/output}}`
 
 - Archive using a specific archive type:
 
-`7z a -t {{zip|gzip|bzip2|tar|...}} {{archived}} {{path/to/file}}`
+`7z a -t {{zip|gzip|bzip2|tar|...}} {{archived.7z}} {{path/to/file}}`
 
 - List available archive types:
 
@@ -24,4 +28,4 @@
 
 - List the contents of an archive file:
 
-`7z l {{archived}}`
+`7z l {{archived.7z}}`