feat: add initial support for server-sent events

[JKRhb]

This PR adds an initial implementation of server-sent events via the sse_channel package to the HTTP binding.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 5.00000% with 19 lines in your changes missing coverage. Please review.

Project coverage is 62.95%. Comparing base (e8373bf) to head (a31de5c).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/src/binding_http/http_subscription.dart	0.00%	17 Missing ⚠️
lib/src/binding_http/http_client.dart	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #200      +/-   ##
==========================================
- Coverage   63.45%   62.95%   -0.50%     
==========================================
  Files          78       79       +1     
  Lines        2301     2319      +18     
==========================================
  Hits         1460     1460              
- Misses        841      859      +18     

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