Clarify that .sz refers to Google's Snappy format

It needs to be disambiguated from the unfortunately named
SZ compression, see https://szcompressor.org/.

Fixes #563

README.md

@@ -111,7 +111,7 @@ Output:
 
 # Supported formats
 
-| Format    | `.tar` | `.zip` | `.gz` | `.xz`, `.lzma` | `.bz`, `.bz2` | `.lz4` | `.sz` | `.zst` |
+| Format    | `.tar` | `.zip` | `.gz` | `.xz`, `.lzma` | `.bz`, `.bz2` | `.lz4` | `.sz` (Snappy) | `.zst` |
 |:---------:|:---:|:---:|:---:|:---:|:---:|:---:|:---:|:---:|
 | Supported | ✓ | ✓¹ | ✓² | ✓ | ✓ | ✓ | ✓² | ✓ |
 

src/cli/args.rs

@@ -5,7 +5,7 @@ use clap::{Parser, ValueHint};
 // Ouch command line options (docstrings below are part of --help)
 /// A command-line utility for easily compressing and decompressing files and directories.
 ///
-/// Supported formats: tar, zip, gz, xz/lzma, bz/bz2, lz4, sz, zst.
+/// Supported formats: tar, zip, gz, xz/lzma, bz/bz2, lz4, sz (Snappy), zst.
 ///
 /// Repository: https://github.com/ouch-org/ouch
 #[derive(Parser, Debug, PartialEq)]