[IMP] web_widget_progressbar_gradient: Add inverse option

Allows to reverse the gradient rendering

web_widget_progressbar_gradient/readme/CONTRIBUTORS.md

@@ -1,2 +1,3 @@
 - Denis Roussel <denis.roussel@acsone.eu>
 - Jacques-Etienne Baudoux <je@bcim.be>
+- Souheil Bejaoui <souheil.bejaoui@acsone.eu>

web_widget_progressbar_gradient/readme/DESCRIPTION.md

@@ -2,4 +2,10 @@ This module allows to display progress bars with colorized gradient bar.
 The color will increase following value from green passing per yellow
 and finishing to red.
 
+- Normal rendering:
+
 ![Progressbar Gradient](../static/description/progressbar_gradient.png)
+
+- Reverse rendering:
+
+![Progressbar Inverse Gradient](../static/description/progressbar_gradient_inverse.png)

web_widget_progressbar_gradient/readme/USAGE.md

@@ -1 +1,3 @@
 - When declaring a progressbar field, use the 'progressbar_color' widget.
+- Add the inverse option to reverse the colors on the progress bar field:
+    ``options="{'inverse': true}"``