npm-root: add page

[canonnizq]

• The page(s) are in the correct platform directories: common, linux, osx, windows, sunos, android, etc.
• The page(s) have at most 8 examples.
• The page description(s) have links to documentation or a homepage.
• The page(s) follow the content guidelines.
• The page(s) follow the style guide.
• The PR title conforms to the recommended templates.
• Version of the command being documented (if known): 10.9.0

[tldr-bot]

The build for this PR failed with the following error(s):

pages/common/npm-root.md:6: TLDR002 A single space should precede a sentence
pages/common/npm-root.md:6: TLDR015 Example descriptions should start with a capital letter
pages/common/npm-root.md:10: TLDR002 A single space should precede a sentence
pages/common/npm-root.md:10: TLDR015 Example descriptions should start with a capital letter

Please fix the error(s) and push again.