docs: Update the Nodejs CI configurations section

[Pradumnasaraf]

Description

• Specify the type of secret needed to be created, as GitHub now has two kinds of secrets under Secrets and variables - Environment and Repository secret.
• Add the missing command to commit the changes, etc in Run the following commands.. section.
• Update the button text to "Test your deployment" to match the sidebar text (like other language docs).
• Improve the context of a couple of sentences.

Reviews

• Technical review
• Editorial review
• Product review

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[craig-osterhout]

Thank you. LGTM.