v4.1 (#11)

- Add `Json` module to return JSON strings and write JSON as it's read to a `PipeWriter`
- Add `docfx`-based documentation to allow how-to docs and API docs to be generated on the same site

Reviewed-on: #11

doc-template/public/main.css

@@ -0,0 +1,4 @@
+article h2 {
+    border-bottom: solid 1px gray;
+    margin-bottom: 1rem;
+}