Make error messages more consistent

package.json

@@ -1,7 +1,7 @@
 {
   "name": "github-contribution-api",
   "description": "Scrape contribution data of a Github user",
-  "version": "4.6.2",
+  "version": "4.6.3",
   "author": "Jonathan Gruber <[email protected]>",
   "license": "MIT",
   "private": true,

src/scrape.ts

@@ -152,11 +152,11 @@ const parseDay = (
   };
 
   if (!attr.date) {
-    throw Error('Unable to parse date attribute.');
+    throw Error('Unable to parse contribution date attribute.');
   }
 
   if (!attr.level) {
-    throw Error('Unable to parse level attribute.');
+    throw Error('Unable to parse contribution level attribute.');
   }
 
   let count = 0;
@@ -236,6 +236,6 @@ export async function scrapeGitHubContributions(
 
 export class UserNotFoundError extends Error {
   constructor(username: string) {
-    super(`User '${username}' not found`);
+    super(`User "${username}" not found.`);
   }
 }