Update Merge Conflicts Lesson

[wvmitchell]

Lesson to be updated: Merge Conflicts

Summary of changes needed:

• The current lesson points to a video which is out of date compared to new versions of VSCode
• VSCode uses the newer, 3 way editor
• Recommendation is to use a different video that shows students how to use this resource

Lesson creation guidelines (also on FE Hub)

• Lesson Preparation Foundations
• 4 Pillars of Remote Instruction
• Instructional Values
• Culturally Responsive Teaching

[letakeane]

PR: https://github.com/turingschool/front-end-curriculum/pull/748