fix: Add typescript type defs in esm build (#985)

build/esm.js

@@ -1,6 +1,7 @@
 const fs = require('fs')
 const path = require('path')
 const util = require('util')
+const { ncp } = require('ncp')
 
 const { promisify } = util
 
@@ -15,6 +16,10 @@ const localeDir = path.join(process.env.PWD, 'esm/locale');
       const result = readFile.replace("'dayjs'", "'../index'")
       await promisify(fs.writeFile)(filePath, result, 'utf8')
     })
+
+    ncp('./types/', './esm', (err) => {
+      if (err) { throw err }
+    })
   } catch (e) {
     console.error(e) // eslint-disable-line no-console
   }