Minor documentation fix - links to node12 and node14 in README.md

[ggrussenmeyer]

Description

Fixed hyperlinks to node12 and node14 templates source code so that they are located in the matching template row.

Motivation and Context

Minor documentation issue that can be confusing.

• I have raised an issue to propose this change (required)

Which issue(s) this PR fixes

Fixes #250.

How Has This Been Tested?

• Browsed README.md in the adequate branch on github.com ;
• Clicked the links ;
• Verified that the correct directory was displayed.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Version change (see: Impact to existing users)

Impact to existing users

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s
• I have added tests to cover my changes.
• All new and existing tests passed.

[alexellis]

Approved. Thank you