Add Readme file to ui-action component

src/plugins/ui_actions/public/cell_actions/README.md

@@ -0,0 +1,17 @@
+This package provides a uniform interface for displaying UI actions for a cell.
+For the `CellActions` component to work, it must be wrapped by `CellActionsContextProvider`. Ideally, the wrapper should stay on the top of the rendering tree.
+
+Example:
+```JSX
+<CellActionsContextProvider
+    // call uiActions.getTriggerCompatibleActions(triggerId, data)
+    getCompatibleActions={getCompatibleActions}>
+    ...
+    <CellActions mode={CellActionsMode.HOVER_POPOVER} triggerId={MY_TRIGGER_ID} config={{ field: 'fieldName', value: 'fieldValue', fieldType: 'text' }}>
+        Hover me
+    </CellActions>
+</CellActionsContextProvider>
+
+```
+
+`CellActions` component will display all compatible actions registered for the trigger id.