Initial commit: Elm tutorial for JavaScript developers

This tutorial includes:
- 7 progressive lessons covering Elm fundamentals
- Exercises with starter code
- Solutions for exercises
- Final project: Task Manager app with localStorage persistence

Topics covered:
- Basic syntax and types
- Functions and functional programming concepts
- The Elm Architecture (Model-View-Update)
- Lists and Maybe types
- HTTP requests and JSON decoding
- Ports for JavaScript interop

exercises/03-temperature/src/Main.elm

@@ -0,0 +1,100 @@
+module Main exposing (main)
+
+{-| Exercise 3: Temperature Converter
+
+Build a temperature converter:
+
+Exercise 3.1: Convert Celsius to Fahrenheit (F = C × 9/5 + 32)
+Exercise 3.2: Add Fahrenheit to Celsius conversion
+Exercise 3.3: Handle invalid input gracefully
+
+Run with: elm reactor
+Then open http://localhost:8000/src/Main.elm
+
+-}
+
+import Browser
+import Html exposing (Html, div, input, text)
+import Html.Attributes exposing (placeholder, value)
+import Html.Events exposing (onInput)
+
+
+
+-- MODEL
+
+
+type alias Model =
+    { celsius : String
+    }
+
+
+init : Model
+init =
+    { celsius = ""
+    }
+
+
+
+-- UPDATE
+
+
+type Msg
+    = UpdateCelsius String
+
+
+update : Msg -> Model -> Model
+update msg model =
+    case msg of
+        UpdateCelsius value ->
+            { model | celsius = value }
+
+
+
+-- HELPER FUNCTIONS
+
+
+celsiusToFahrenheit : Float -> Float
+celsiusToFahrenheit c =
+    -- TODO: Implement the conversion formula
+    0
+
+
+
+-- VIEW
+
+
+view : Model -> Html Msg
+view model =
+    let
+        fahrenheit =
+            case String.toFloat model.celsius of
+                Just c ->
+                    -- TODO: Call celsiusToFahrenheit and format the result
+                    "TODO"
+
+                Nothing ->
+                    "Enter a valid number"
+    in
+    div []
+        [ input
+            [ placeholder "Enter Celsius"
+            , value model.celsius
+            , onInput UpdateCelsius
+            ]
+            []
+        , text " °C = "
+        , text fahrenheit
+        ]
+
+
+
+-- MAIN
+
+
+main : Program () Model Msg
+main =
+    Browser.sandbox
+        { init = init
+        , update = update
+        , view = view
+        }