Add support for non ascii path

[SukkaW]

What is the PR for?

The PR is trying to fix #99

What happened?

Well, wrangler publish will store the original path & filename inside Workers KV, just like the screenshot shows:

However, new URL will encode path by default:

const url = new URL('https://example.com/你好/');
url.href;
// "https://example.com/%E4%BD%A0%E5%A5%BD/"
url.pathname;
// "/%E4%BD%A0%E5%A5%BD/"

Then?

Since I am a Cloudflare Enterprise customer, the first thing I do is to open a ticket at Cloudflare Support. Then the Technical Support Engineer told me it is a known issue and no ETA for fixes. Then I asked if any workarounds could be provided and received "the workaround that I am aware of which is not ideal, is to migrate away pathes".

Well, I can fix the issue myself.

Instead of letting wrangler-cli encoding filename, I create this PR to let kv-asset-handler handle encoded URL by decoding path before handling.

Is the changes tested?

At least I have added a test case.