zstd, unzstd: update page; zstd{cat,mt}: add alias page (#10683)

pages/common/unzstd.md

@@ -1,16 +1,7 @@
 # unzstd
 
-> Decompress files with Zstandard compression.
-> More information: <https://github.com/facebook/zstd>.
+> This command is an alias of `zstd --decompress`.
 
-- Decompress files:
+- View documentation for the original command:
 
-`unzstd {{path/to/file1.ztd path/to/file2.ztd ...}}`
-
-- Decompress a file into a specific output file:
-
-`unzstd {{path/to/compressed.ztd}} -o {{path/to/extracted_file}}`
-
-- Display information about a compressed file:
-
-`unzip --list {{path/to/file.zst}}`
+`tldr zstd`