Added bar.space as an optional property to ChartConfiguration interface (#22804)

* Added bar.space as an optional property to ChartConfiguration interface

This property lets you to set space between bars in bar charts

* Add tests for new property

types/c3/c3-tests.ts

@@ -619,7 +619,8 @@ function chart_bar() {
             width: {
                 ratio: 0.5, // this makes bar width 50% of length between ticks
                 max: 50 // this limits maximum width of bar to 50px
-            }
+            },
+            space: 10 // this adds space between bars in bar charts
             // or
             // width: 100 // this makes bar width 100px
         }

types/c3/index.d.ts

@@ -178,6 +178,10 @@ export interface ChartConfiguration {
          * Set if min or max value will be 0 on bar chart.
          */
         zerobased?: boolean;
+        /**
+         * Set space between bars in bar charts
+         */
+        space?: number;
     };
 
     pie?: {