Update issue templates

.github/ISSUE_TEMPLATE/chain-added---updated---deprecated.md

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+---
+name: Chain Added / Updated / Deprecated
+about: Let us know of any change in supported chains or their data services.
+title: Added/Update/Deprecate [CHAIN]
+labels: ''
+assignees: SoA432, DominicF96
+
+---
+
+## Add/Update Chain
+
+Please provide the following information. See https://github.com/pinax-network/chains/issues/1 for more information.
+
+```json
+{
+  "id": "alfajores",
+  "index": 4,
+  "graph_id": null,
+  "name": "Alfajores",
+  "url": "https://celo.org",
+  "alt_names": [],
+  "mainnet": "celo",
+  "standard": "erc20",
+  "block_type": {
+    "label": "sf.ethereum.type.v2.Block",
+    "url": "https://buf.build/streamingfast/firehose-ethereum/docs/main:sf.ethereum.type.v2"
+  },
+  "is_testnet": true,
+  "supported_services": {
+    "firehose": false,
+    "substreams": false,
+    "rpc": false
+  }
+}
+```
+
+## Deprecate Chain
+
+Please provide the date of the deprecation.