Update /ja/index.html and /en/index.html article code samples.

Fixed to use the latest API in the article code samples.
Correspond to the latest BiquadFilterNode API

The type property in BiquadFilterNode is number type in old API.
But, this is string type in the latest API.
Therefore, this update added code for wrapping this difference.
Merge pull request #1273 from Korilakkuma/my-work

Update  /ja/index.html, /en/index.html and /js/filter-sample.js