fix(components): [watermark] missing the CSS file (#14564)

closed #14560

global.d.ts

@@ -95,6 +95,7 @@ declare module '@vue/runtime-core' {
     ElDescriptionsItem: typeof import('element-plus')['ElDescriptionsItem']
     ElResult: typeof import('element-plus')['ElResult']
     ElSelectV2: typeof import('element-plus')['ElSelectV2']
+    ElWatermark: typeof import('element-plus')['ElWatermark']
   }
 
   interface ComponentCustomProperties {

packages/components/index.ts

@@ -69,6 +69,7 @@ export * from './tree-select'
 export * from './tree-v2'
 export * from './upload'
 export * from './virtual-list'
+export * from './watermark'
 
 // plugins
 export * from './infinite-scroll'