Makes frontmatter functions available for use (#51)

* feat: adds yaml frontmatter support

* exports frontmatter functions for use in applications

Author: HomeroKemmerich

src/index.ts

@@ -1,14 +1,12 @@
 export * from './defaults';
-export * from './rendering';
-export * from './rendering.types';
-export * from './shared.types';
 export * from './renderers/blockquote';
 export * from './renderers/bold';
 export * from './renderers/code';
 export * from './renderers/codeblock';
 export * from './renderers/dl';
 export * from './renderers/emoji';
 export * from './renderers/footnote';
+export * from './renderers/frontmatter';
 export * from './renderers/h1';
 export * from './renderers/h2';
 export * from './renderers/h3';
@@ -31,3 +29,6 @@ export * from './renderers/table';
 export * from './renderers/tasks';
 export * from './renderers/text';
 export * from './renderers/ul';
+export * from './rendering';
+export * from './rendering.types';
+export * from './shared.types';