docs(ref): endpoint update for v1.3

[thephez]

• Add getEvonodesProposedEpochBlocksByIds (feat: query block count per Evonode proposed in any given epoch platform#2114)
• Add getEvonodesProposedEpochBlocksByRange (feat: query block count per Evonode proposed in any given epoch platform#2114)
• Add getIdentitiesBalances (feat: query many identity balances at a time platform#2112)

Preview build: https://dash-docs--81.org.readthedocs.build/projects/platform/en/81/docs/reference/dapi-endpoints.html#platform-grpc-service

[thephez]

Merging as these are usable on v1.3 evonodes currently even though the the protocol upgrade hasn't happened yet.

E.g.,

grpcurl -proto protos/platform/v0/platform.proto -d '{
   "v0": {
     "epoch": 0, "limit": 10, "prove": false
   }
}' 149.28.241.190:443 org.dash.platform.dapi.v0.Platform/getEvonodesProposedEpochBlocksByRange