Harmonize formatting and capitalization of stdin/stdout/stderr

pages/common/parallel.md

@@ -7,7 +7,7 @@
 
 `parallel gzip ::: {{file1}} {{file2}} {{file3}}`
 
-- Read arguments from stdin, run 4 jobs at once:
+- Read arguments from `stdin`, run 4 jobs at once:
 
 `ls *.txt | parallel -j4 gzip`
 
@@ -19,7 +19,7 @@
 
 `{{args}} | parallel -X {{command}}`
 
-- Break stdin into ~1M blocks, feed each block to stdin of new command:
+- Break stdin into ~1M blocks, feed each block to `stdin` of new command:
 
 `cat {{big_file.txt}} | parallel --pipe --block 1M {{command}}`