Merge pull request #60 from clockor2/expose-annotation-writers

fix: expose annotation writers

src/index.ts

@@ -1,5 +1,9 @@
 export { Tree, Node } from './tree';
-export { writeNewick } from './io/writers/newick';
+export {
+  writeNewick,
+  beastAnnotation,
+  nhxAnnotation,
+} from './io/writers/newick';
 export { writeNexus } from './io/writers/nexus';
 export { readNewick, readTreesFromNewick } from './io/readers/newick';
 export { readNexus, readTreesFromNexus } from './io/readers/nexus';