Rewrite the README

Author: skalee

README.md

@@ -1 +1,11 @@
-See the subdirectories.
+Documentation for _Fishial Recognition API v2_ is deployed to GitHub Pages: https://fishial.github.io/devapi/v2/.
+
+## Useful resources
+
+* Jekyll (static site generator):
+    * documentation: https://jekyllrb.com/docs/
+* Just the Docs (Jekyll theme):
+    * documentation: https://just-the-docs.github.io/just-the-docs/
+* Asciidoc (markup language):
+    * quick syntax reference: https://docs.asciidoctor.org/asciidoc/latest/syntax-quick-reference/
+    * documentation: https://docs.asciidoctor.org/asciidoc/latest/