refactor: Tag class support in registerTag()

src/fs/browser.ts

@@ -1,4 +1,4 @@
-import { last } from '../util/underscore'
+import { last } from '../util'
 
 function domResolve (root: string, path: string) {
   const base = document.createElement('base')

src/fs/index.ts

@@ -0,0 +1,2 @@
+export * from './loader'
+export * from './fs'

src/fs/loader.ts

@@ -1,6 +1,5 @@
 import { FS } from './fs'
-import { escapeRegex } from '../util/underscore'
-import { assert } from '../util/assert'
+import { assert, escapeRegex } from '../util'
 
 export interface LoaderOptions {
   fs: FS;

src/fs/node.ts

@@ -1,10 +1,10 @@
-import * as _ from '../util/underscore'
+import { promisify } from '../util'
 import { sep, resolve as nodeResolve, extname, dirname as nodeDirname } from 'path'
 import { stat, statSync, readFile as nodeReadFile, readFileSync as nodeReadFileSync } from 'fs'
 import { requireResolve } from './node-require'
 
-const statAsync = _.promisify(stat)
-const readFileAsync = _.promisify<string, string, string>(nodeReadFile)
+const statAsync = promisify(stat)
+const readFileAsync = promisify<string, string, string>(nodeReadFile)
 
 export async function exists (filepath: string) {
   try {