[E2E] Update the blocks E2E setup guide

[WunderBart]

Changes proposed in this Pull Request:

While setting up the repo for the first time, I encountered some issues with installing Playwright browsers and setting up the e2e env. I've updated the readme with the steps that helped me fix those issues.

Ref: p1707400637260049-slack-C04JMARP9LK

Changelog entry

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Significance

• Patch
• Minor
• Major

Type

• Fix - Fixes an existing bug
• Add - Adds functionality
• Update - Update existing functionality
• Dev - Development related task
• Tweak - A minor adjustment to the codebase
• Performance - Address performance issues
• Enhancement - Improvement to existing functionality

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Comment

[github-actions]

Hi @Aljullu, @imanish003,

Apart from reviewing the code changes, please make sure to review the testing instructions as well.

You can follow this guide to find out what good testing instructions should look like:
https://github.com/woocommerce/woocommerce/wiki/Writing-high-quality-testing-instructions

[github-actions]

Test Results Summary

Commit SHA: c649f59

Test 🧪	Passed ✅	Failed 🚨	Broken 🚧	Skipped ⏭️	Unknown ❔	Total 📊	Duration ⏱️
API Tests	259	0	0	2	0	261	0m 40s
E2E Tests	297	0	0	17	0	314	6m 41s

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To view the full API test report, click here.
To view the full E2E test report, click here.
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[Aljullu]

Thanks for updating the docs, @WunderBart! I left one minor comment, but not a blocker. Besides that, everything LGTM.

By the way, heads-up that you will need to rebase on trunk before merging to get Playwright tests to pass.