chore: Update sentry logo in readme files

[mattjohnsonpint]

Originally #5037. Basing this one on the 7.x branch. Using the purple Sentry logo instead of media queries, due to rendering issues on NPM when the system is configured for dark theme. The purple logo works on both white and black backgrounds.

I also got all the readme's in the repo, not just the root.

Thanks!

#skip-changelog

[AbhiPrasad]

Thanks @mattjohnsonpint!

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	18.72 KB (-7.04% 🔽)
@sentry/browser - ES5 CDN Bundle (minified)	58.51 KB (-9.45% 🔽)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	17.53 KB (-7.04% 🔽)
@sentry/browser - ES6 CDN Bundle (minified)	52.69 KB (-9.11% 🔽)
@sentry/browser - Webpack (gzipped + minified)	19.2 KB (-17.38% 🔽)
@sentry/browser - Webpack (minified)	62.07 KB (-24.05% 🔽)
@sentry/react - Webpack (gzipped + minified)	19.22 KB (-17.43% 🔽)
@sentry/nextjs Client - Webpack (gzipped + minified)	42.9 KB (-10.74% 🔽)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	24.5 KB (-6.06% 🔽)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	23.08 KB (-5.74% 🔽)

[lforst]

Thank you! :)