chore: add landing page redirect flag (#5724)

* chore: add landing page redirect flag

* unused

* fix

src/components/FeatureFlagModal/FeatureFlagModal.tsx

 import { BaseVariant, FeatureFlag, featureFlagSettings, useUpdateFlag } from 'featureFlags'
+import { LandingRedirectVariant, useLandingRedirectFlag } from 'featureFlags/flags/landingRedirect'
 import { Permit2Variant, usePermit2Flag } from 'featureFlags/flags/permit2'
 import { TraceJsonRpcVariant, useTraceJsonRpcFlag } from 'featureFlags/flags/traceJsonRpc'
 import { useAtomValue, useUpdateAtom } from 'jotai/utils'
@@ -208,6 +209,12 @@ export default function FeatureFlagModal() {
         featureFlag={FeatureFlag.permit2}
         label="Permit 2 / Universal Router"
       />
+      <FeatureFlagOption
+        variant={LandingRedirectVariant}
+        value={useLandingRedirectFlag()}
+        featureFlag={FeatureFlag.landingRedirect}
+        label="Landing Page Redirect"
+      />
       <FeatureFlagGroup name="Debug">
         <FeatureFlagOption
           variant={TraceJsonRpcVariant}

src/featureFlags/flags/featureFlags.ts

 export enum FeatureFlag {
   traceJsonRpc = 'traceJsonRpc',
   permit2 = 'permit2',
+  landingRedirect = 'landingRedirect',
 }

src/featureFlags/flags/landingRedirect.ts

+import { BaseVariant, FeatureFlag, useBaseFlag } from '../index'
+
+export function useLandingRedirectFlag(): BaseVariant {
+  return useBaseFlag(FeatureFlag.landingRedirect)
+}
+
+export { BaseVariant as LandingRedirectVariant }