import declaration should not include semicolon or require line end

See https://github.com/Microsoft/vscode/issues/30527

The coffeescript grammar includes the JavaScript grammar.
With the following example:

`import Ember from 'ember'`
# foo bar baz
if true then console.log('qnx')

the JavaScript grammar is used to tokenize what's inside the backward quotes. Problem is that it does not return to the initial state after processing 'ember'. It expects a semicolon or the end of the line. Because of that, the JavaScript grammar scope remains and the rest of the file is colorized also with the JavaScipt grammar.

For supporting embedded cases like this, it would be great if the import declaration rule could end to end with the string literal or any non-expected symbol.

まず、grammar ファイル内の import 宣言ルールを見つけ、issue に埋め込まれている CoffeeScript の例を再現します。JavaScript grammar が import の文字列リテラルをどのように処理し、周囲の grammar に戻るかを確認します。埋め込まれた import が文字列リテラルまたは別の予期しないシンボルで停止し、その後に続く CoffeeScript が JavaScript として色付けされなくなれば完了です。