feat(cozy-device-helper): Add isFlagshipOfflineSupported() method

Since cozy/cozy-flagship-app#1209 the Flagship app can inject the
`offline_available` attribute into WebViews metadata in order to tell
the cozy-app when offline mode is supported

The new `` method can now be used to check this attribute

packages/cozy-device-helper/src/flagship.ts

@@ -16,6 +16,7 @@ export interface FlagshipMetadata {
   biometry_type?: BiometryType
   immersive?: boolean
   navbarHeight?: number
+  offline_available?: boolean
   platform?: Record<string, unknown>
   route?: FlagshipRoutes
   settings_PINEnabled?: boolean
@@ -40,3 +41,6 @@ export const getFlagshipMetadata = (): FlagshipMetadata =>
 
 export const isFlagshipApp = (): boolean =>
   getGlobalWindow()?.cozy?.flagship !== undefined
+
+export const isFlagshipOfflineSupported = (): boolean =>
+  getGlobalWindow()?.cozy?.flagship?.offline_available

packages/cozy-device-helper/src/index.ts

@@ -21,4 +21,8 @@ export { isCordova } from './cordova'
 export { nativeLinkOpen } from './link'
 export { openDeeplinkOrRedirect } from './deeplink'
 
-export { isFlagshipApp, getFlagshipMetadata } from './flagship'
+export {
+  isFlagshipApp,
+  isFlagshipOfflineSupported,
+  getFlagshipMetadata
+} from './flagship'