Package for Sublime Text 3. Insert "use strict" directive to the top of the file.
Via Package Control:
Open Command Palette → Package Control: Install Package → UseStrict
Run command UseStrict: Insert "use strict" to the top of the file and
it will append 'use strict' to the top of the active file.
{
// Whether to insert semicolon after the "use strict" directive
"semicolon": false,
// String quote symbol to use in the "use strict" directive. Can be "'", "\"" or even any string.
"quote_symbol": "'",
}