fix: remove urlsafe-base64 dependency

[lenkan]

In PR #214, I missed that the urlsafe-base64 dependency used the global Buffer object internally. I already had some polyfills added when I tested the change so I missed that we still required the polyfill.

There are a few solutions to this.

• Re-introduce the polyfill but also set globalThis.Buffer = import("buffer").Buffer.
• Stop using "Buffer" completely, just use Uint8Array which is available in both browser and node.js runtime.
• Implement base64url encode/decode using the imported buffer buffer module.

I think the first one is a hack and an anti-pattern to taint global namespace in a library. The second one is a bit too much work for a quick fix. The last one is a good compromise in my opinion, so I did that. Ideally, the buffer module should support base64 url encode/decode but the PR for that has not been merged for some time: feross/buffer#314.

I took some code and test cases from the node.js ecosystem and replaced the urlsafe-base64 dependency with an internal module that uses the buffer package.

Let me know what you think. Can also go with option 1 if you prefer. But a fix is needed to avoid forcing users to polyfill for themselves.

[codecov]

Codecov Report

Attention: Patch coverage is 84.61538% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 82.86%. Comparing base (e2b2f6e) to head (d534ee3).

Files	Patch %	Lines
src/keri/core/base64.ts	83.33%	2 Missing ⚠️
src/keri/core/httping.ts	50.00%	1 Missing ⚠️
src/keri/core/indexer.ts	75.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           development     #218   +/-   ##
============================================
  Coverage        82.86%   82.86%           
============================================
  Files               46       47    +1     
  Lines             4190     4202   +12     
  Branches          1044     1047    +3     
============================================
+ Hits              3472     3482   +10     
- Misses             689      691    +2     
  Partials            29       29           

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[psteniusubi]

Less dependencies is better in my opinion. Ultimately I think we should get rid of Buffer completely.

[pfeairheller]

I think this is a good compromise. I doubt there will be any innovations in Base64 encoding/decoding we'll have to keep up with!