XFA - Get line height from the font

- when the CSS line-height property is set to 'normal' then the value depends of the user agent. So use a line height based on the font itself and if for any reasons this value is not available use 1.2 as default.
  - it's a partial fix for https://bugzilla.mozilla.org/show_bug.cgi?id=1717681.

src/core/xfa/utils.js

@@ -24,6 +24,13 @@ const dimConverters = {
 };
 const measurementPattern = /([+-]?[0-9]+\.?[0-9]*)(.*)/;
 
+function stripQuotes(str) {
+  if (str.startsWith("'") || str.startsWith('"')) {
+    return str.slice(1, str.length - 1);
+  }
+  return str;
+}
+
 function getInteger({ data, defaultValue, validate }) {
   if (!data) {
     return defaultValue;
@@ -206,4 +213,5 @@ export {
   getRelevant,
   getStringOption,
   HTMLResult,
+  stripQuotes,
 };