docs: add browser bundling guide

[rajanpanth]

Summary

• document how to bundle JSR-published Standard Library TypeScript for browsers
• use the recommended esbuild-deno-loader integration with a complete entry point and build script
• explain browser-compatibility declarations and deno.json import-map discovery

Closes #4586

Validation

• deno fmt --check README.md
• ran the documented example with Deno 2.9.5 and confirmed esbuild generated dist/main.js
• git diff --check

[CLAassistant]

All committers have signed the CLA.

[tomas-zijdemans]

Thanks for picking this up, #4586 sat open for a long time. A few suggestions from me:

• CI is red: deno task test type-checks ts fences in markdown too. Mark both snippets ```ts ignore (FAQ.md has the convention).
• Prefer deno bundle --platform browser -o dist/main.js main.ts as the primary path. @kt3k suggested the loader before deno bundle returned in 2.4.
• Swap the base64 example. encodeBase64 is most likely on its way out of std now that Uint8Array.fromBase64 exists. You could use something from @std/text or @std/html instead.
• The deno.json note is off: the loader resolves config from cwd or an explicit configPath, not the entry point. Moot if you switch to deno bundle.
• nit: await esbuild.stop().

[rajanpanth]

Thanks for the detailed review. I updated the guide to:

• use deno bundle --platform browser -o dist/main.js main.ts as the primary path
• mark both TypeScript snippets as ts ignore for markdown type-checking
• replace the base64 example with @std/html/entities
• remove the incorrect deno.json loader discovery note
• change the esbuild example to await esbuild.stop()

I also ran git diff --check locally. I could not run deno task test on this machine because deno is not available on PATH here, so I’ll watch CI for the updated commit.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.03%. Comparing base (ca58f94) to head (cfa73c8).

Additional details and impacted files

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##             main    #7289   +/-   ##
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  Coverage   95.03%   95.03%           
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  Files         617      617           
  Lines       51637    51637           
  Branches     9359     9359           
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  Hits        49075    49075           
  Misses       2021     2021           
  Partials      541      541           

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