Flutter/fix missing hb style get value

Resolves: https://github.com/rive-app/rive-flutter/issues/437

Diffs=
c084b3c608 Flutter/fix missing hb style get value (#8665)
5d65f91a4d Draggables (aka scrolling) (#8493)
043dbff5a7 Nnnn data bind fixes part 2 (#8637)
8251557144 make nested animation properties bindable (#8642)
f846fe28e9 Layout display & animation duration keyable (#8553)

Co-authored-by: Gordon <pggordonhayes@gmail.com>

.rive_head

@@ -1 +1 @@
-42b2ac0cecc712a89d9e896d16c1d0875581aff2
+c084b3c60822506bec6410597e7bf4d16ef21d90

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.13.20
+
+- Fix: Windows/Linux building. Undefined symbol `hb_style_get_value`, see issue [437](https://github.com/rive-app/rive-flutter/issues/437)
+  
 ## 0.13.19
 
 - Adds the `isTouchScrollEnabled` property to `RiveAnimation` and `Rive` widgets. When `true` allows scrolling behavior to occur on Rive widgets when a touch/drag action is performed on touch-enabled devices. Defauls to `false`, which means Rive will "absorb" the pointer down event and a scroll cannot be triggered if the touch occured within a Rive Listener area. Setting to `true` will impact Rive's capability to handle multiple gestures simultaneously.

pubspec.yaml

@@ -1,5 +1,5 @@
 name: rive
-version: 0.13.19
+version: 0.13.20
 homepage: https://rive.app
 description: Rive Flutter Runtime. This package provides runtime functionality for playing back and interacting with animations built with the Rive editor available at https://rive.app.
 repository: https://github.com/rive-app/rive-flutter
@@ -21,7 +21,7 @@ dependencies:
   http: ">=0.13.3 <2.0.0"
   meta: ^1.3.0
   plugin_platform_interface: ^2.0.2
-  rive_common: 0.4.14
+  rive_common: 0.4.15
 dev_dependencies:
   flutter_test:
     sdk: flutter