Charset is not set on index.html for GraphiQL

[GTRanger]

Description

The index.html for GraphiQL should have <meta charset="UTF-8"/> in the head of the HTML since the CSS it uses has UTF-8 encoded characters (i.e. the fold/unfold arrows) that do not render properly otherwise.

Expected Behavior

Uncollapsed and collapsed arrows should render as "▾" and "▸" respectively.

Actual Behavior

Uncollapsed and collapsed arrows render as "â–¾" and "â–¸" respectively.