style-guide: add guidelines for standard streams; fix remaining pages (#11196)

* readonly, {un,}compress, zbarcam: use proper syntax for IO streams

* style-guide: add guidelines for standard streams

* duckdb, perl: add backticks around stdin and stdout

pages/linux/uncompress.md

@@ -11,10 +11,10 @@
 
 `uncompress -f {{path/to/file1.Z path/to/file2.Z ...}}`
 
-- Write to standard output (no files are changed and no `.Z` files are created):
+- Write to `stdout` (no files are changed and no `.Z` files are created):
 
 `uncompress -c {{path/to/file1.Z path/to/file2.Z ...}}`
 
-- Verbose mode (write to standard error about percentage reduction or expansion):
+- Verbose mode (write to `stderr` about percentage reduction or expansion):
 
 `uncompress -v {{path/to/file1.Z path/to/file2.Z ...}}`