Rephrase why command description and minor fixes

pages/common/yarn.md

@@ -6,15 +6,15 @@
 
 `yarn global add {{module_name}}`
 
-- Install all dependencies referenced in the package.json:
+- Install all dependencies referenced in the package.json file:
 
 `yarn`
 
-- Install a module and save it as a dependency to the package.json. Add --dev to save as a dev dependency:
+- Install a module and save it as a dependency to the package.json file (add --dev to save as a dev dependency):
 
 `yarn add {{module_name}}@{{version}}`
 
-- Uninstall a module and remove it from the package.json:
+- Uninstall a module and remove it from the package.json file:
 
 `yarn remove {{module_name}}`
 
@@ -22,6 +22,6 @@
 
 `yarn init`
 
-- Identify why the module is installed and list other modules that depend on it:
+- Identify whether a module is a dependency and list other modules that depend upon it:
 
 `yarn why {{module_name}}`