feat(platforms): enable web platform support

[levischechter]

Description

Use GrpcOrGrpcWebClientChannel class from grpc package so also browsers will be able to communicate
with the GrpcWeb server of cosmos-sdk based blockchains.

Closes #172

Checklist

• Targeted PR against correct branch -yup.
• #140
• manual testing by me. tests includes android and web platforms against an cosmos-sdk based blockchain grpc and grpcweb servers respectfully.
• Run make format - nop.
• Run make lint - nop.
• no need as nothing else should be made by the developer for the default behavior.
• left it to the maintainers.
• Re-reviewed Files changed in the Github PR explorer and added meaningful comments - nop.

[codecov]

Codecov Report

Patch coverage: 17.64% and project coverage change: -0.69 ⚠️

Comparison is base (292e83a) 76.70% compared to head (454f0e5) 76.02%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #194      +/-   ##
==========================================
- Coverage   76.70%   76.02%   -0.69%     
==========================================
  Files          26       26              
  Lines         674      684      +10     
==========================================
+ Hits          517      520       +3     
- Misses        157      164       +7     

Impacted Files	Coverage Δ
lib/transactions/sender/tx_sender.dart	69.23% <0.00%> (ø)
lib/transactions/signer/tx_signer.dart	75.55% <ø> (ø)
lib/wallet/network_info.dart	52.11% <18.75%> (-3.63%)	⬇️

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[RiccardoM]

Thanks for your contribution @levischechter! May I ask what's the difference between this and #172? I was actually waiting someone to test that before merging it

[levischechter]

@RiccardoM In the previous one I didn't used the right ClientChannel as the abstract class, and I didn't enabled the option to use separate hosts for the grpc and the grpcweb protocols

[RiccardoM]

Thank you so much for your contribution! 🙏