Fix/remove metamask success error

[yizhang0901]

there's a smol bug on the protect site where adding the protect RPC via the frontend always pops up an error even though the RPC still gets successfully added. you can see in this video

i'm offering a $100 bug bounty for anyone who's able to prevent an error from popping up when the RPC is successfully added.

[2bf]

Submitted a focused fix in PR #47: #47

It keeps user-rejection behavior unchanged, but treats the known MetaMask success-after-add provider errors as successful so the UI shows "Added to Metamask" instead of surfacing a false error alert. Local verification passed with npm run lint and npm run build.