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.

Start by locating the import declaration rule in the grammar files and reproduce the embedded CoffeeScript example from the issue. Check how the JavaScript grammar handles the import string literal and returns to the surrounding grammar. Done means the embedded import stops at the string literal or another non-expected symbol, while the following CoffeeScript is no longer JavaScript-colored.