Add markdown format support (#25)

Co-authored-by: Dawid Dziurla <dawidd0811@gmail.com>

node_modules/showdown/CREDITS.md

@@ -0,0 +1,48 @@
+Credits
+=======
+  - Showdown v1
+    * [Estevão Santos](https://github.com/tivie)
+    * [Pascal Deschênes](https://github.com/pdeschen)
+
+  - Showdown v0
+    * [Corey Innis](http://github.com/coreyti):<br/>
+      Original GitHub project maintainer
+    * [Remy Sharp](https://github.com/remy/):<br/>
+      CommonJS-compatibility and more
+    * [Konstantin Käfer](https://github.com/kkaefer/):<br/>
+      CommonJS packaging
+    * [Roger Braun](https://github.com/rogerbraun):<br/>
+      Github-style code blocks
+    * [Dominic Tarr](https://github.com/dominictarr):<br/>
+      Documentation
+    * [Cat Chen](https://github.com/CatChen):<br/>
+      Export fix
+    * [Titus Stone](https://github.com/tstone):<br/>
+      Mocha tests, extension mechanism, and bug fixes
+    * [Rob Sutherland](https://github.com/roberocity):<br/>
+      The idea that lead to extensions
+    * [Pavel Lang](https://github.com/langpavel):<br/>
+      Code cleanup
+    * [Ben Combee](https://github.com/unwiredben):<br/>
+      Regex optimization
+    * [Adam Backstrom](https://github.com/abackstrom):<br/>
+      WebKit bugfix
+    * [Pascal Deschênes](https://github.com/pdeschen):<br/>
+      Grunt support, extension fixes + additions, packaging improvements, documentation
+    * [Estevão Santos](https://github.com/tivie)<br/>
+      Bug fixing and late maintainer
+    * [Hannah Wolfe](https://github.com/ErisDS)<br/>
+      Bug fixes
+    * [Alexandre Courtiol](https://github.com/acourtiol)<br/>
+      Bug fixes and build optimization
+    * [Karthik Balakrishnan](https://github.com/torcellite)<br/>
+      Support for table alignment
+    * [rheber](https://github.com/rheber)<br/>
+      Cli
+      
+
+  - Original Project
+    * [John Gruber](http://daringfireball.net/projects/markdown/)<br/>
+      Author of Markdown
+    * [John Fraser](http://attacklab.net/)<br/>
+      Author of Showdown