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[bot]]

Codecov Report

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

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

Additional details and impacted files

```diff @@ 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](https://app.codecov.io/gh/alan-sdk/alan.dart/pull/194?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=alan-sdk) | Coverage Δ | | |---|---|---| | [lib/transactions/sender/tx\_sender.dart](https://app.codecov.io/gh/alan-sdk/alan.dart/pull/194?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=alan-sdk#diff-bGliL3RyYW5zYWN0aW9ucy9zZW5kZXIvdHhfc2VuZGVyLmRhcnQ=) | `69.23% <0.00%> (ø)` | | | [lib/transactions/signer/tx\_signer.dart](https://app.codecov.io/gh/alan-sdk/alan.dart/pull/194?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=alan-sdk#diff-bGliL3RyYW5zYWN0aW9ucy9zaWduZXIvdHhfc2lnbmVyLmRhcnQ=) | `75.55% <ø> (ø)` | | | [lib/wallet/network\_info.dart](https://app.codecov.io/gh/alan-sdk/alan.dart/pull/194?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=alan-sdk#diff-bGliL3dhbGxldC9uZXR3b3JrX2luZm8uZGFydA==) | `52.11% <18.75%> (-3.63%)` | :arrow_down: |

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[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! :pray: