config: Add Instagram link button

[takumiando]

This commit adds Instagram link button.
The icon is imported from the official logo pack.

https://www.meta.com/ja-jp/brand/resources/instagram/instagram-brand/

[yashi]

The icon has extra data others don't have.

the d= part is

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You can test it on https://yqnn.github.io/svg-path-editor/

You don't need transform= and others, too.

[yashi]

Looks much better. Thanks.