Fix IDB interface

Author: chuanqisun

index.d.ts

@@ -259,10 +259,9 @@ declare module '@isomorphic-git/lightning-fs' {
       db?: FS.IDB
     }
     export interface IDB {
-      constructor(dbname: string, storename: string): IDB
       saveSuperblock(sb: Uint8Array): TypeOrPromise<void>
       loadSuperblock(): TypeOrPromise<FS.SuperBlock>
-      loadFile(inode: number): TypeOrPromise<Uint8Array>
+      readFile(inode: number): TypeOrPromise<Uint8Array>
       writeFile(inode: number, data: Uint8Array): TypeOrPromise<void>
       wipe(): TypeOrPromise<void>
       close(): TypeOrPromise<void>