Add download button (#45)

Resolves #22

index.html

@@ -343,6 +343,8 @@ <h1>CodeMeta generator v3.0</h1>
             title="Checks the codemeta.json file below is valid, and displays errors." />
         <input type="button" id="importCodemeta" value="Import codemeta.json" disabled
             title="Fills the fields above based on the codemeta.json file below." />
+        <a id="downloadCodemeta"><input type="button" value="Download codemeta.json" disabled
+                  title="Download the codemeta.json file as displayed below." /></a>
     </form>
 
     <p id="errorMessage">

js/codemeta_generation.js

@@ -435,3 +435,12 @@ function loadStateFromStorage() {
         importCodemeta();
     }
 }
+
+function downloadCodemeta() {
+    const codemetaText = document.querySelector('#codemetaText').innerText;
+    const blob = new Blob([codemetaText], {type: 'application/json'});
+    const url = URL.createObjectURL(blob);
+    document.querySelector('#downloadCodemeta').href = url;
+    document.querySelector('#downloadCodemeta').download = "codemeta.json";
+    URL.revokeObjectURL(url);
+}

js/dynamic_form.js

@@ -221,6 +221,10 @@ function initCallbacks() {
     document.querySelector('#importCodemeta')
         .addEventListener('click', importCodemeta);
 
+    document.querySelector('#downloadCodemeta input').disabled = false;
+    document.querySelector('#downloadCodemeta input')
+        .addEventListener('click', downloadCodemeta);
+
     document.querySelector('#inputForm')
         .addEventListener('change', () => generateCodemeta());