feat: add Hello World theme

themes/hello-world/go.mod

@@ -2,4 +2,4 @@ module github.com/wowchemy/wowchemy-hugo-modules/themes/hello-world
 
 go 1.15
 
-require github.com/wowchemy/wowchemy-hugo-modules/wowchemy latest
+require github.com/wowchemy/wowchemy-hugo-modules/wowchemy v0.0.0-20201107233547-e18ecbbff3a2