Update Plasma mainnet & devnet (#7668)

* Add Plasma Mainnet (9745) and update Testnet configuration

- Add Plasma Mainnet with chain ID 9745
- Update Plasma Testnet (9746) explorer URL and shortName
- Add Plasma icon (SVG) for both networks
- Empty RPC/explorer for mainnet pending live deployment

* Fix validation: use empty explorers array for mainnet

The validator requires explorer entries to have valid URLs.
Since the mainnet explorer isn't live yet, using an empty array instead.

* Update Plasma chains: fix mainnet shortname, add devnet

* Remove explorer from Plasma Devnet

* Fix trailing newline for Plasma mainnet

---------

Co-authored-by: Frederik Bolding <[email protected]>
Co-authored-by: Hans Behrens <{"message":"Not Found","documentation_url":"https://docs.github.com/rest/users/emails#list-email-addresses-for-the-authenticated-user","status":"404"}>

Author: hwbehrens

_data/chains/eip155-9745.json

@@ -1,17 +1,23 @@
 {
   "name": "Plasma Mainnet",
   "chain": "Plasma",
-  "rpc": [],
+  "rpc": ["https://rpc.plasma.to"],
   "faucets": [],
   "nativeCurrency": {
     "name": "Plasma",
     "symbol": "XPL",
     "decimals": 18
   },
   "infoURL": "https://plasma.to",
-  "shortName": "plasma-mainnet",
+  "shortName": "plasma",
   "chainId": 9745,
   "networkId": 9745,
   "icon": "plasma",
-  "explorers": []
+  "explorers": [
+    {
+      "name": "Routescan",
+      "url": "https://plasmascan.to",
+      "standard": "EIP3091"
+    }
+  ]
 }

_data/chains/eip155-9747.json

@@ -0,0 +1,17 @@
+{
+  "name": "Plasma Devnet",
+  "chain": "Plasma",
+  "rpc": ["https://devnet-rpc.plasma.to"],
+  "faucets": [],
+  "nativeCurrency": {
+    "name": "Devnet Plasma",
+    "symbol": "XPL",
+    "decimals": 18
+  },
+  "infoURL": "https://plasma.to",
+  "shortName": "plasma-devnet",
+  "chainId": 9747,
+  "networkId": 9747,
+  "icon": "plasma",
+  "explorers": []
+}