Improve README.md accessibility for screen readers

[throwaway-d]

1. The "issue" and "pull request" badges are removed because they're obvious that you can already see the counters on GitHub.
2. Add height = '20' for the remaining badges. https://web.dev/optimize-cls/#images-without-dimensions
3. Improve alt texts of the badges (the alt texts on ## Screenshots is still not worked on yet)
4. Add height = '353' for the screenshots https://web.dev/optimize-cls/#images-without-dimensions
5. Remove some unnecessary trailing slashes on img elements README.md https://github.com/validator/validator/wiki/Markup-%C2%BB-Void-elements

Related Issue

• closes https://github.com/ThioJoe/YT-Spammer-Purge/issues/713

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

Checklist:

• [x] My code follows the style guidelines of this project and I have read CONTRIBUTING.md
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] Any dependent changes have been merged and published in downstream modules
• [x] I have checked my code and corrected any misspellings

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Screenshots

Original	Updated

[throwaway-d]

I'm very newbie to GitHub and PRs. Please kindly guide me if anything's wrong. I mostly stay on Codeberg and create issues. (https://github.com/ThioJoe/YT-Spammer-Purge/discussions/994)

[throwaway-d]

I will try to convince him since this impacts accessibility of blind people.

[KendallDoesCoding]

I will try to convince him since this impacts accessibility of blind people.

ok 🤷

[throwaway-d]

for now

Even he didn't really confirm that he would keep it forever. He was just procrastinating at that time.

[throwaway-d]

A good guide about alt text: https://www.w3.org/WAI/tutorials/images

[throwaway-d]

@ThioJoe It has been many months already. Can you please merge my PR?