an error "UnhandledPromiseRejectionWarning: Error: EILSEQ, Illegal byte sequence" occurred when using Japanese characters on loadImage function

## Issue or Feature

As the title suggests.

## Steps to Reproduce

```js
const { loadImage } = require('canvas')
const myimg = loadImage('あ.jpg')
```
The results are as follows:
```
(node:23792) UnhandledPromiseRejectionWarning: Error: EILSEQ, Illegal byte sequence 'あ.jpg'
at setSource (C:\Users\user\WebstormProjects\myProject\node_modules\canvas\lib\image.js:91:13)
at Image.set (C:\Users\user\WebstormProjects\myProject\node_modules\canvas\lib\image.js:62:9)
at C:\Users\user\WebstormProjects\myProject\node_modules\canvas\index.js:34:15
at new Promise ()
at loadImage (C:\Users\user\WebstormProjects\myProject\node_modules\canvas\index.js:23:10)
at Object. (C:\Users\user\WebstormProjects\myProject\main.js:2:15)
at Module._compile (internal/modules/cjs/loader.js:1236:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:1257:10)
at Module.load (internal/modules/cjs/loader.js:1085:32)
at Function.Module._load (internal/modules/cjs/loader.js:950:14)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:23792) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:23792) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
```
So is it not supported using Japanese or other languages for a file name? I confirmed It can be reproduced when using Korean or Chinese characters too.
thanks.

## Your Environment
* Version of node-canvas : canvas@2.7.0
* Environment : node v14.6.0, Windows 10 Pro x64 version 20H2