feat: unix adaptor for elm called starmelon

Introduce starmelon, a program for executing elm functions with input
from files and writing the output back to files.

Support evaluating 4 types of values and 12 types of functions.
```elm
x : String
x : Bytes
x : VirtualDom.Node msg
x : Json.Encode.Value

f : String -> String
f : String -> Bytes
f : String -> VirtualDom.Node msg
f : String -> Json.Encode.Value
f : Bytes -> String
f : Bytes -> Bytes
f : Bytes -> VirtualDom.Node msg
f : Bytes -> Json.Encode.Value
f : Json.Encode.Value -> String
f : Json.Encode.Value -> Bytes
f : Json.Encode.Value -> VirtualDom.Node msg
f : Json.Encode.Value -> Json.Encode.Value
```

My target use case for starmelon is generating html files. It is nice
to be able to write parameterized framgents of markup in multiple
modules and then compose them into a final value. I also have in mind
attempting to replace helm (kubernetes pacakge manager) because I hate
how error prone its string based templating language is.

examples/single-page/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "single-page"
+version = "0.1.0"
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[lib]
+crate-type = [ "dylib" ]
+
+[dependencies]
+

examples/single-page/elm.json

@@ -0,0 +1,25 @@
+{
+    "type": "application",
+    "source-directories": [
+        "src"
+    ],
+    "elm-version": "0.19.1",
+    "dependencies": {
+        "direct": {
+            "elm/browser": "1.0.2",
+            "elm/core": "1.0.5",
+            "elm/html": "1.0.0",
+            "elm/svg": "1.0.1"
+        },
+        "indirect": {
+            "elm/json": "1.1.3",
+            "elm/time": "1.0.0",
+            "elm/url": "1.0.0",
+            "elm/virtual-dom": "1.0.2"
+        }
+    },
+    "test-dependencies": {
+        "direct": {},
+        "indirect": {}
+    }
+}

examples/single-page/src/Foo/Main.elm

@@ -0,0 +1,14 @@
+module Foo.Main exposing (view)
+
+import Html exposing (Html, div, text)
+import Array exposing (Array)
+
+type alias Model =
+    { a : Int
+    , b : Array Int
+    }
+
+view : Model -> Html msg
+view model =
+    div []
+        [ text "Hello world" ]

examples/single-page/src/Main.elm

@@ -0,0 +1,19 @@
+module Main exposing (view, view2)
+
+import Html exposing (Html, div, text)
+import Svg exposing (Svg, svg)
+import Array exposing (Array)
+
+type alias Model =
+    { a : Int
+    , b : Array Int
+    }
+
+view2 : String -> Svg msg
+view2 model =
+    svg [] []
+
+view : String -> Html msg
+view model =
+    div []
+        [ text <| "Hello world" ++ model ]

examples/single-page/src/lib.rs

@@ -0,0 +1,6 @@
+#![crate_type = "dylib"]
+
+#[no_mangle]
+pub fn foobar() -> i32 {
+    42
+}

examples/single-page/starmelon

@@ -0,0 +1 @@
+../../../../../target/debug/starmelon