Add Additional Resource: Inspecting HTML and CSS

[Fiattarone]

Pesticide is an excellent extension that will surely help learners understand the boundaries of their elements.

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

Complete the following checkboxes ONLY IF they are applicable to your PR. You can complete them later if they are not currently applicable:

• [ ] I have previewed all lesson files included in this PR with the Markdown preview tool to ensure the Markdown content is formatted correctly
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1. Because:

Closes #XXXXX Because this can help learners visually understand transparent/invisible element boundaries.

2. This PR:

• Add additional resource, browser plugin/extension

3. Additional Information:

[Fiattarone]

This might actually be better in the following lesson on Box Models (sorry!). Let me know if that is more appropriate and I'll happily transfer the resource.

[zachmmeyer]

Hello! Thanks for contributing to the curriculum. I'm trying to figure out how this helps more than opening up the devtools of your browser and looking at individual elements. I understand that it will show all of the elements. Instead of having users install a browser specific extension, why not just follow this: https://stackoverflow.com/a/40310910

[Fiattarone]

@zachmmeyer That is an excellent point that I'll be bringing home myself. Thanks!