Use default import for files using `raw-loader`

## Description

There are a number of files where we use 

```
import * as description form './something.md';
``` 

instead of a simple 

```
import description from './something.md';
```

It's surprising that these both work, but let's try to be consistent and use the [expected default export](https://github.com/webpack-contrib/raw-loader).

## The list

```
git grep -E "import \\*.*md['\"]"

src/components/base/avatar/avatar.documentation.js
src/components/base/avatar_labeled/avatar_labeled.documentation.js
src/components/base/avatar_link/avatar_link.documentation.js
src/components/base/breadcrumb/breadcrumb.documentation.js
src/components/base/button/button.documentation.js
src/components/base/button_group/button_group.documentation.js
src/components/base/datepicker/datepicker.documentation.js
src/components/base/daterange_picker/daterange_picker.documentation.js
src/components/base/dropdown/dropdown.documentation.js
src/components/base/dropdown/dropdown_divider.documentation.js
src/components/base/dropdown/dropdown_header.documentation.js
src/components/base/dropdown/dropdown_item.documentation.js
src/components/base/form/form_checkbox/form_checkbox.documentation.js
src/components/base/form/form_group/form_group.documentation.js
src/components/base/form/form_input/form_input.documentation.js
src/components/base/form/form_radio/form_radio.documentation.js
src/components/base/form/form_select/form_select.documentation.js
src/components/base/form/form_textarea/form_textarea.documentation.js
src/components/base/friendly_wrap/friendly_wrap.documentation.js
src/components/base/icon/icon.documentation.js
src/components/base/infinite_scroll/infinite_scroll.documentation.js
src/components/base/intersperse/intersperse.documentation.js
src/components/base/link/link.documentation.js
src/components/base/loading_icon/loading_icon.documentation.js
src/components/base/modal/modal.documentation.js
src/components/base/new_button/new_button.documentation.js
src/components/base/new_dropdown/dropdown_divider.documentation.js
src/components/base/new_dropdown/dropdown_header.documentation.js
src/components/base/new_dropdown/dropdown_item.documentation.js
src/components/base/new_dropdown/new_dropdown.documentation.js
src/components/base/paginated_list/paginated_list.documentation.js
src/components/base/pagination/pagination.documentation.js
src/components/base/search_box_by_click/search_box_by_click.documentation.js
src/components/base/search_box_by_type/search_box_by_type.documentation.js
src/components/base/skeleton_loading/skeleton_loading.documentation.js
src/components/base/sorting/sorting.documentation.js
src/components/base/sorting/sorting_item.documentation.js
src/components/base/table/table.documentation.js
src/components/base/tabs/tab/tab.documentation.js
src/components/base/tabs/tabs/tabs.documentation.js
src/components/base/toast/toast.documentation.js
src/components/base/tooltip/tooltip.documentation.js
src/components/charts/area/area.documentation.js
src/components/charts/chart/chart.documentation.js
src/components/charts/column/column.documentation.js
src/components/charts/discrete_scatter/discrete_scatter.documentation.js
src/components/charts/heatmap/heatmap.documentation.js
src/components/charts/legend/legend.documentation.js
src/components/charts/line/line.documentation.js
src/components/charts/series_label/series_label.documentation.js
src/components/charts/single_stat/single_stat.documentation.js
src/components/charts/stacked_column/stacked_column.documentation.js
src/components/charts/tooltip/tooltip.documentation.js
src/components/regions/dashboard_skeleton/dashboard_skeleton.documentation.js
src/components/regions/empty_state/empty_state.documentation.js
src/directives/resize_observer/resize_observer.documentation.js
```

Story points: 1.0