Doc: CHANGELOG.md and README.md updated

Author: Vectrex

CHANGELOG.md

@@ -1,3 +1,6 @@
+## [v1.3.7]
+- Absolutely or fixed positioned components (`modal`, `message-toast`, `confirm`, `datepicker`, `autocomplete`) and label created with `v-floating-label` directive use CSS vars to determine their stacked position and can therefore be configured
+
 ## [v1.3.6]
 - The `modal` component got a more robust layout and a better default class for the container element
 

README.md

@@ -59,3 +59,12 @@ Style them in your projects main CSS file with
     --color-vxvue-alt: -...;
 ```
 
+Stacking of absolutely or fixed positioned elements use the following CSS variables to determine their position in the z-index stack:
+
+```
+--zIndex-confirm: 1000;
+--zIndex-toast: 900;
+--zIndex-dropdown: 800;
+--zIndex-label: 100;
+--zIndex-modal: 600;
+```