Clarify: Links and Images Lesson

[Fiattarone]

Clarified foundational information as to not confuse learners when they encounter key/name-only HTML attributes later on.

Complete the following REQUIRED checkboxes:

• [x] I have thoroughly read and understand The Odin Project Contributing Guide
• [x] The title of this PR follows the location of change: brief description of change format, e.g. Intro to HTML and CSS lesson: Fix link text

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1. Because:

Closes #XXXXX Because this could be confusing to people who move forward expecting all HTML attributes to be key-value paired.

2. This PR:

• Clarified that not all HTML attributes are key-value paired as succinctly as I could.

3. Additional Information: