[useSort] Provide API to clear sorting at column level (#1476)

* [useSort] Provide API to clear sorting at column level

* updated docs

docs/api.md

@@ -458,6 +458,8 @@ The following properties are available on every `Column` object returned by the
   - This function is used to resolve any props needed for this column's UI that is responsible for toggling the sort direction when the user clicks it.
   - You can use the `getSortByToggleProps` hook to extend its functionality.
   - Custom props may be passed. **NOTE: Custom props may override built-in sortBy props, so be careful!**
+- `clearSorting: Function() => void`
+  - This function can be used to programmatically clear the sorting for this column.
 - `isSorted: Boolean`
   - Denotes whether this column is currently being sorted
 - `sortedIndex: Int`

src/plugin-hooks/useSortBy.js

@@ -173,7 +173,18 @@ function useMain(instance) {
 
     if (column.canSort) {
       column.toggleSortBy = (desc, multi) =>
-        toggleSortBy(column.id, desc, multi)
+        toggleSortBy(column.id, desc, multi);
+      
+      column.clearSorting = () => {
+        return setState(old => {
+          const { sortBy } = old;
+          const newSortBy = sortBy.filter(d => d.id !== column.id);
+          return {
+            ...old,
+            sortBy: newSortBy,
+          }
+        }, actions.sortByChange);
+      };
     }
 
     column.getSortByToggleProps = props => {