Add supported Luci builders for flutter repo (#62445)

dev/README.md

@@ -5,3 +5,24 @@ course, they may be interesting if you are curious.
 
 The tests in this directory are run in the `framework_tests_misc-*`
 shards.
+
+## Luci builder file
+`try_builders.json` and `prod_builders.json` contain the
+supported luci try/prod builders for engine. They follow format:
+```json
+{
+    "builders":[
+        {
+            "name":"xxx1",
+            "repo":"flutter"
+        },
+        {
+            "name":"xxx2",
+            "repo":"flutter",
+            "taskName":"yyy2"
+        }
+    ]
+}
+```
+These files will be mainly used in [`flutter/cocoon`](https://github.com/flutter/cocoon)
+to trigger/update flutter luci tasks.

dev/prod_builders.json

+{
+   "builders":[
+      {
+         "name":"Linux",
+         "repo":"flutter",
+         "taskName":"linux_bot"
+      },
+      {
+         "name":"Mac",
+         "repo":"flutter",
+         "taskName":"mac_bot"
+      },
+      {
+         "name":"Windows",
+         "repo":"flutter",
+         "taskName":"windows_bot"
+      },
+      {
+         "name":"Linux Coverage",
+         "repo":"flutter"
+      }
+   ]
+}

dev/try_builders.json

+{
+   "builders":[
+      {
+         "name":"Linux",
+         "repo":"flutter",
+         "taskName":"linux_bot"
+      },
+      {
+         "name":"Windows",
+         "repo":"flutter",
+         "taskName":"windows_bot"
+      }
+   ]
+}