[1.11.x] Fixed #27900 -- Made escapejs escape backticks for use in ES6 template literals.

Backport of 6ae1b04fb5 from master

django/utils/html.py

@@ -61,6 +61,7 @@ _js_escapes = {
     ord('='): '\\u003D',
     ord('-'): '\\u002D',
     ord(';'): '\\u003B',
+    ord('`'): '\\u0060',
     ord('\u2028'): '\\u2028',
     ord('\u2029'): '\\u2029'
 }

tests/utils_tests/test_html.py

@@ -142,6 +142,7 @@ class TestUtilsHtml(SimpleTestCase):
                 'paragraph separator:\u2029and line separator:\u2028',
                 'paragraph separator:\\u2029and line separator:\\u2028'
             ),
+            ('`', '\\u0060'),
         )
         for value, output in items:
             self.check_output(f, value, output)