MultiCombobox: Add basic docs and make story public (#100806)

* MutliCombobox: Add basic docs and make story public

* Apply suggestions from code review

Co-authored-by: Alex Khomenko <Clarity-89@users.noreply.github.com>

---------

Co-authored-by: Alex Khomenko <Clarity-89@users.noreply.github.com>

packages/grafana-ui/src/components/Combobox/MultiCombobox.mdx

@@ -0,0 +1,20 @@
+import { Meta, Preview, ArgTypes } from '@storybook/blocks';
+
+import { MultiCombobox } from './MultiCombobox';
+
+<Meta title="MDX|MultiCombobox" component={MultiCombobox} />
+
+# MultiCombobox
+
+The behavior of the MultiCombobox is similar to that of the Combobox, but it allows you to select multiple options. For all non-multi behaviors, see the Combobox documentation.
+
+## "All" functionality
+
+Use the prop `enableAllOption` to show the "All" option.
+
+- If no filtering is applied, selecting "All" will select all options, returning the same array as the `options` prop.
+- With filtering, selecting "All" will choose the filtered subset of options.
+
+## Props
+
+<ArgTypes of={MultiCombobox} />

packages/grafana-ui/src/components/Combobox/MultiCombobox.story.tsx

@@ -6,12 +6,18 @@ import { ComponentProps } from 'react';
 import { Field } from '../Forms/Field';
 
 import { MultiCombobox } from './MultiCombobox';
+import mdx from './MultiCombobox.mdx';
 import { generateOptions, fakeSearchAPI, generateGroupingOptions } from './storyUtils';
 import { ComboboxOption } from './types';
 
 const meta: Meta<typeof MultiCombobox> = {
   title: 'Forms/MultiCombobox',
   component: MultiCombobox,
+  parameters: {
+    docs: {
+      page: mdx,
+    },
+  },
 };
 
 const loadOptionsAction = action('options called');