Feat: Support xDai network provider and subgraph url

[0xGabi]

This PR adds support for xDai default provider and subgraph URL.

Until now users need to use the library like:

const provider = new ethers.providers.JsonRpcProvider(
  'https://xdai.poanetwork.dev',
  {
    name: 'xdai',
    chainId: 100,
    ensAddress: '0xaafca6b0c89521752e559650206d7c925fd0e530',
  }
)

const org = await connect(
  daoAddress,
  [
    'thegraph',
    { orgSubgraphUrl: 'https://api.thegraph.com/subgraphs/name/1hive/aragon-xdai' },
  ],
  { chainId: 100, readProvider: ethereum }
)

With this change we can do:

const org = await connect(ORG_ADDRESS, 'thegraph', {
  chainId: 100,
})

[codecov]

Codecov Report

Merging #119 into master will decrease coverage by 0.13%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #119      +/-   ##
==========================================
- Coverage   24.12%   23.98%   -0.14%     
==========================================
  Files          59       59              
  Lines        1032     1038       +6     
  Branches      167      170       +3     
==========================================
  Hits          249      249              
- Misses        783      789       +6     

Flag	Coverage Δ
#unittests	23.98% <0.00%> (-0.14%)	⬇️

Impacted Files	Coverage Δ
packages/connect-core/src/entities/Organization.ts	0.00% <0.00%> (ø)
packages/connect-core/src/params.ts	0.00% <0.00%> (ø)
packages/connect-thegraph/src/connector.ts	57.77% <0.00%> (-2.69%)	⬇️

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