fix(fab, tab-button): rtl alignment in safari and firefox (#26986)

resolves #22739

core/src/themes/ionic.mixins.scss

@@ -326,6 +326,19 @@
       right: $end;
     }
   } @else {
+    @at-root {
+      @supports (inset-inline-start: 0) {
+        & {
+          inset-inline-start: $start;
+          inset-inline-end: $end;
+        }
+      }
+    }
+
+    // TODO FW-3766
+    @at-root {
+      @supports not (inset-inline-start: 0) {
+        & {
           @include ltr() {
             left: $start;
             right: $end;
@@ -339,6 +352,9 @@
           }
         }
       }
+    }
+  }
+}
 
 // Add position for all directions
 // @param {string} $top