fix(README): update "sections below" reference

[pshields]

This PR updates the "sections below" reference to point to the installation docs, since the details and alternatives are not present in the sections below of the README.

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature (please, look at the "Scope of the project" section in the README.md file)
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

The documentation refers to "sections below", but the sections below do not contain additional details or alternatives for installing rules_nodejs.

Issue Number: N/A

What is the new behavior?

Link to the docs page that contains the additional details and alternatives.

Does this PR introduce a breaking change?

• Yes
• No