feat: Add unit tests (#21)

Tests are mostly complete (though some are failing -- to be fixed in the
async/await refactor.

Also refactored, fixed bugs found while testing, and added ability to
type `pf;m` instead of `pf;member`.

---------

Co-authored-by: Aster Fialla <asterfialla@gmail.com>

src/helpers/utils.js

@@ -0,0 +1,29 @@
+import {enums} from '../enums.js'
+
+const u = {};
+
+u.debounce = function(func, delay) {
+    let timeout = null;
+    return function (...args) {
+        clearTimeout(timeout);
+        timeout = setTimeout(() => func(...args), delay);
+    };
+}
+
+/**
+ * Checks if an uploaded picture is in the right format.
+ *
+ * @async
+ * @param {string} imageUrl - The url of the image
+ * @throws {Error} When loading the profile picture from a URL doesn't work, or it fails requirements.
+ */
+u.checkImageFormatValidity = async function (imageUrl) {
+    const acceptableImages = ['image/png', 'image/jpg', 'image/jpeg', 'image/webp'];
+    await fetch(imageUrl).then(r => r.blob()).then(blobFile => {
+        if (blobFile.size > 1000000 || !acceptableImages.includes(blobFile.type)) throw new Error(enums.err.PROPIC_FAILS_REQUIREMENTS);
+    }).catch((error) => {
+        throw new Error(`${enums.err.PROPIC_CANNOT_LOAD}: ${error.message}`);
+    });
+}
+
+export const utils = u;