xDai chain support by default

[vbaranov]

Inspired by https://twitter.com/rstormsf/status/1192275093054881792?s=19

xDai chain resources: https://www.xdaichain.com/
xDai explorer: https://blockscout.com/poa/xdai/
xDai bridge: https://dai-bridge.poa.network

[rstormsf]

@whymarrh any feedback on this?

[whymarrh]

Hey, @vbaranov, thanks for putting this together. (@rstormsf thanks for the ping.) As I commented over on the Pocket Network PR, the network list can't be extended to include everyone's networks and we don't have a way of honestly choosing among all the possible networks. As noted in the Twitter thread linked in the OP, our forthcoming plugin system may very well be a way to introduce some extensibility to MetaMask's understanding of networks.

I'm closing this for now, but #3604 and #5101 are relevant here, as ideally we should have a way to allow sites (or plugins) to add new networks and we welcome new ideas on this front.

[anxolin]

When will we see this PR in a release?

[github-actions]

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[anxolin]

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