Added the ability to set the label and value key names

You can now set the names of the `label` and `value` keys in the options. They default to `label` and `value` to not break the current behavior, but you can also set them to `null`, so that you can use a simple object instead of an array of objects, just like in bootstrap-4-autocomplete.

Examples:
```
const ac = new Autocomplete(field, {
    data: [{name: "entry1", text: "The first entry"}, {name: "entry2", text: "The second entry"}],
    label: "name",
    value: "text",
    onSelectItem: ({label, value}) => {
        console.log("user selected:", label, value);
    }
});



const ac = new Autocomplete(field, {
    data: {entry1: "The first entry", entry2: "The second entry"},
    label: null,
    value: null,
    onSelectItem: ({label, value}) => {
        console.log("user selected:", label, value);
    }
});
```

1 files changed, 13 insertions, 4 deletions

diff --git a/autocomplete.js b/autocomplete.js
index 7a9f151..016f8c3 100644
--- a/autocomplete.js
+++ b/autocomplete.js
@@ -3,6 +3,8 @@ const DEFAULTS = {
   maximumItems: 5,
   highlightTyped: true,
   highlightClass: 'text-primary',
+  label: 'label',
+  value: 'value'
 };
 
 class Autocomplete {
@@ -15,7 +17,7 @@ class Autocomplete {
     field.setAttribute('data-bs-toggle', 'dropdown');
     field.classList.add('dropdown-toggle');
 
-    const dropdown = ce(`<div class="dropdown-menu" ></div>`);
+    const dropdown = ce(`<div class="dropdown-menu"></div>`);
     if (this.options.dropdownClass)
       dropdown.classList.add(this.options.dropdownClass);
 
@@ -84,10 +86,17 @@ class Autocomplete {
     const items = this.field.nextSibling;
     items.innerHTML = '';
 
+    const keys = Object.keys(this.options.data);
+
     let count = 0;
-    for (let i = 0; i < this.options.data.length; i++) {
-      const {label, value} = this.options.data[i];
-      const item = {label, value};
+    for (let i = 0; i < keys.length; i++) {
+      const key = keys[i];
+      const entry = this.options.data[key];
+      const item = {
+          label: this.options.label ? entry[this.options.label] : key,
+          value: this.options.value ? entry[this.options.value] : entry
+      };
+
       if (item.label.toLowerCase().indexOf(lookup.toLowerCase()) >= 0) {
         items.appendChild(this.createItem(lookup, item));
         if (this.options.maximumItems > 0 && ++count >= this.options.maximumItems)