feat(foundations/variables and operators): add several examples and clarify a few points

[NikitaRevenco]

Because

Lesson could see some improvement. This is the first lesson where learners are introduced to javascript. It should be a lot more beginner-friendly

A lot of these changes are subjective. Feel free to suggest certain changes to be reverted.

This PR

• Grouped / removed many points in the Learning outcomes
  • I believe the current list is too long and could be intimidating to someone who has never heard about javascript before
• Added a few examples here and there
• Removed paragraph talking about the fact that JS can be run outside of browser
  • Learners wouldn't even know that it is possible to do so. Adds unnecessary complexity in my opinion
• Lesson overview items are now statements instead of questions
• Instructions on how to open the dev tools are improved
• Moved many things to assignment
• Removed an additional resource relating to var
  • learners would not know about scope, functions or control flow at this point
• Many other small improvements

Issue

Closes #XXXXX

Additional Information

Pull Request Requirements

• I have thoroughly read and understand The Odin Project Contributing Guide
• 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
• The Because section summarizes the reason for this PR
• The This PR section has a bullet point list describing the changes in this PR
• If this PR addresses an open issue, it is linked in the Issue section
• If any lesson files are included in this PR, they have been previewed with the Markdown preview tool to ensure it is formatted correctly
• If any lesson files are included in this PR, they follow the Layout Style Guide

[ManonLef]

Hi @NikitaRevenco

I'm sorry about the delay. It looks like the file has been edited a bit in the meantime as well.
Could you re-request a review when the merge conflicts have been solved? I'll try to find some time for the review soon.

[NikitaRevenco]

I've resolved the conflicts

[fortypercenttitanium]

Nice work, please address my comments and we will take another look.

[fortypercenttitanium]

Good work, just a few more small suggestions

[fortypercenttitanium]

Thank you!!

Taken care of