*: fix errors reported by languagetool (#6069)

pages/common/optipng.md

@@ -1,17 +1,17 @@
 # optipng
 
-> PNG image file optimization utility.
+> PNG file optimization utility.
 > More information: <http://optipng.sourceforge.net>.
 
 - Compress a PNG with default settings:
 
 `optipng {{path/to/file.png}}`
 
-- Compress a PNG with best compression:
+- Compress a PNG with the best compression:
 
 `optipng -o{{7}} {{path/to/file.png}}`
 
-- Compress a PNG with fastest compression:
+- Compress a PNG with the fastest compression:
 
 `optipng -o{{0}} {{path/to/file.png}}`