bootloaderInstructions: add videos

[dlech]

This adds videos to show how to enter bootloader mode.

Issue: pybricks/support#728

[codecov-commenter]

Codecov Report

Base: 69.99% // Head: 69.58% // Decreases project coverage by -0.40% ⚠️

Coverage data is based on head (9a28383) compared to base (ec06b00).
Patch coverage: 60.60% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1364      +/-   ##
==========================================
- Coverage   69.99%   69.58%   -0.41%     
==========================================
  Files         189      189              
  Lines        4539     4666     +127     
  Branches      913      948      +35     
==========================================
+ Hits         3177     3247      +70     
- Misses       1342     1402      +60     
+ Partials       20       17       -3     

Impacted Files	Coverage Δ
src/blueprintjs-icons.js	0.00% <ø> (ø)
src/components/ViewHeightSensor.tsx	50.00% <ø> (ø)
src/editor/lib.ts	100.00% <ø> (ø)
src/editor/pybricksMicroPython.ts	47.61% <ø> (ø)
src/editor/sagas.ts	37.63% <ø> (ø)
src/editor/untitledHint.ts	97.22% <ø> (ø)
src/fileStorage/actions.ts	100.00% <ø> (ø)
src/fileStorage/index.ts	100.00% <ø> (ø)
src/index.tsx	0.00% <ø> (ø)
src/settings/Settings.tsx	75.00% <0.00%> (-6.40%)	⬇️
... and 13 more

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[laurensvalk]

I could try looking at the details later tonight (not in the next hour), but if you’re happy with how it looks I’m all 🟢 for a beta/RC release.

We can tweak the videos and text next week as needed.