Feature : Add config to set the filmstrip background opaque

Author: Axel Prola

docs/dev-guide/configuration.md

@@ -915,6 +915,19 @@ filmstrip: {
 }
 ```
 
+### filmstripBackgroundOpaque
+
+type: `Boolean`
+
+Default: **unset**
+
+If true force the filmstrip container background to have an opacity of 1
+
+```javascript
+filmstripBackgroundOpaque: true
+```
+
+
 ## Face Landmarks
 
 ### faceLandmarks