Make find as a clean architecture

src/content/client/FindClient.ts

@@ -0,0 +1,25 @@
+import * as messages from '../../shared/messages';
+
+export default interface FindClient {
+  getGlobalLastKeyword(): Promise<string | null>;
+
+  setGlobalLastKeyword(keyword: string): Promise<void>;
+
+  // eslint-disable-next-line semi
+}
+
+export class FindClientImpl implements FindClient {
+  async getGlobalLastKeyword(): Promise<string | null> {
+    let keyword = await browser.runtime.sendMessage({
+      type: messages.FIND_GET_KEYWORD,
+    });
+    return keyword as string;
+  }
+
+  async setGlobalLastKeyword(keyword: string): Promise<void> {
+    await browser.runtime.sendMessage({
+      type: messages.FIND_SET_KEYWORD,
+      keyword: keyword,
+    });
+  }
+}