feat(table): add header cell component

This adds a HeaderCell Component which provides basic styling for table headers.

packages/index.ts

@@ -1,3 +1,3 @@
 export { Badge } from "./badge";
 export { BadgeButton } from "./badge";
-export { Column, Table, Cell } from "./table";
+export { Column, Table, Cell, HeaderCell } from "./table";

packages/table/components/HeaderCell.tsx

@@ -0,0 +1,7 @@
+import { default as Cell } from "./Cell";
+import styled from "react-emotion";
+
+export default styled(Cell)`
+  text-transform: uppercase;
+  font-weight: bold;
+`;

packages/table/index.ts

@@ -1,3 +1,4 @@
 export { default as Table } from "./components/Table";
 export { default as Column } from "./components/Column";
 export { default as Cell } from "./components/Cell";
+export { default as HeaderCell } from "./components/HeaderCell";