[#3213] Fix link typo in 02-conventions.mdx

[mosesintech]

===:clipboard: PR Checklist :clipboard:===

• [x] :pushpin: issue exists in github for these changes
• [x] :microscope: existing tests still pass
• [x] :see_no_evil: code conforms to the style guide
• [x] :triangular_ruler: new tests written and passing / old tests updated with new scenario(s)
• [x] :page_facing_up: changelog entry added (or not needed)

==================

Closes #3213

Changes:

• add preceding / to Resources link

[eonarheim]

@mosesintech Thanks for the fix! Much appreciated