Add translate="no" for prevent auto-translating code

[no-yan]

Currently, when you try to machine-translate websites in the Tour of Go, the code editor is also translated.
This is not ideal for learning code.

In this Issue, I propose to use the translate attribute in html.
By adding translate="no" to the code editor, the code will not be translated, but the explanations will be translated without problems.
(Note that the way of using this attribute with a code block is also how it is described in the specification.)

This addition would be helpful for learners who want to learn in a language that has no translations yet, or who are having trouble with incomplete translations.

[no-yan]

Here is a example of diff.
On the left, you can see that the` code is not translated.

(The left has 'translate="no"' and the right is the original)