add parsing font size from string

app/assets/sample_data.json

@@ -451,7 +451,7 @@
    },
    {
       "attributes": {
-         "size": 12.0
+         "size": "small"
       },
       "insert": "Small"
    },
@@ -460,7 +460,7 @@
    },
    {
       "attributes": {
-         "size": 35.0
+         "size": "large"
       },
       "insert": "Large"
    },
@@ -469,10 +469,34 @@
    },
    {
       "attributes": {
-         "size": 60.0
+         "size": "huge"
       },
       "insert": "Huge"
    },
+   {
+      "attributes": {
+         "size": "15.0"
+      },
+      "insert": "font size 15"
+   },
+   {
+      "insert": " "
+   },
+   {
+      "attributes": {
+         "size": "35"
+      },
+      "insert": "font size 35"
+   },
+   {
+      "insert": " "
+   },
+   {
+      "attributes": {
+         "size": "50"
+      },
+      "insert": "font size 50"
+   },
    {
       "insert": "\n"
    }

app/lib/pages/home_page.dart

@@ -71,7 +71,7 @@ class _HomePageState extends State<HomePage> {
         onPressed: (){
          int option =  Random().nextInt(30);
           print(option);
-          _controller.formatSelection(SizeAttribute(option.toDouble()));
+          _controller.formatSelection(SizeAttribute("${option.toDouble()}"));
         },
       ),
       body: RawKeyboardListener(

lib/models/documents/attribute.dart

@@ -206,8 +206,8 @@ class FontAttribute extends Attribute<double> {
   FontAttribute(double val) : super('font', AttributeScope.INLINE, val);
 }
 
-class SizeAttribute extends Attribute<double> {
-  SizeAttribute(double val) : super('size', AttributeScope.INLINE, val);
+class SizeAttribute extends Attribute<String> {
+  SizeAttribute(String val) : super('size', AttributeScope.INLINE, val);
 }
 
 class LinkAttribute extends Attribute<String> {

lib/widgets/text_line.dart

@@ -137,6 +137,7 @@ class TextLine extends StatelessWidget {
 
     Attribute size = textNode.style.attributes[Attribute.size.key];
     if (size != null && size.value != null) {
+
       switch (size.value) {
         case 'small':
           res = res.merge(defaultStyles.sizeSmall);
@@ -148,6 +149,11 @@ class TextLine extends StatelessWidget {
           res = res.merge(defaultStyles.sizeHuge);
           break;
         default:
+          double fontSize = double.tryParse(size.value);
+          if(fontSize!=null){
+            res = res.merge(TextStyle(fontSize: fontSize));
+          }
+          else
           throw "Invalid size ${size.value}";
       }
     }