Add http examples for example DB endpoints (#12)

* Add http examples for example DB endpoints

* address PR comments

http/database_read_example.http

@@ -0,0 +1,15 @@
+@hostname=localhost
+@port=4444
+@address=http://{{hostname}}:{{port}}
+
+### Get a document by ID.
+# Returns an `ExampleDocument`, or `null` if there is no document with the given ID:
+# {
+#     _id: u32,
+#     string: String,
+#     number: i32
+# }
+#
+# @prompt id The ID of the document to get
+
+GET {{address}}/read/{{id}}

http/database_write_example.http

@@ -0,0 +1,19 @@
+@hostname=localhost
+@port=4444
+@address=http://{{hostname}}:{{port}}
+
+### Insert or update a document (of type `ExampleDocument`).
+# Returns HTTP status code only.
+#
+# @prompt id The ID of the document to insert or update
+# @prompt string An arbitrary string to store in the document
+# @prompt number An arbitrary 32-bit integer to store in the document
+
+PUT {{address}}/write
+Content-Type: application/json
+
+{
+	"_id": {{id}},
+	"string": "{{string}}",
+	"number": {{number}}
+}