Add companion runtime gateway client foundation

src/companion/index.ts

@@ -0,0 +1,25 @@
+export {
+  CompanionRuntimeClient,
+  GatewayRpcError,
+} from './runtimeClient.js';
+
+export type {
+  CompanionRuntimeClientOptions,
+  RegisterNodeInput,
+  ListNodesInput,
+  SetNodeStatusInput,
+  SetNodeLocationInput,
+  SetNodePushTokenInput,
+  NodeRegisterResult,
+  NodeCapabilitiesResult,
+  NodeStatusSetResult,
+  NodeLocationSetResult,
+  NodeLocationGetResult,
+  NodePushTokenSetResult,
+  SystemCapabilitiesResult,
+  SystemNodesResult,
+  SystemNodeEntry,
+  NodeLocation,
+  NodeStatus,
+  NodePushSummary,
+} from './runtimeClient.js';