Lighten light mode slightly (#105)

Partially undoing #101, but only partially.

Author: mreichhoff

public/css/hanzi-graph.css

@@ -1,8 +1,8 @@
 :root {
-    --background-color: #f6f6f6;
+    --background-color: #fafafa;
     --primary-font-color: rgba(0, 0, 0, 0.87);
     --primary-font: Roboto, Helvetica, Arial, sans-serif;
-    --primary-font-weight: 400;
+    --primary-font-weight: 300;
     --primary-header-height: 50px;
     --primary-header-font-size: 30px;
     --secondary-header-font-size: 30px;

public/index.html

@@ -7,7 +7,7 @@
     <meta name="description"
         content="Learn Chinese by exploring the relationships between characters alongside examples that illustrate their use.">
     <meta name="viewport" content="width=device-width, initial-scale=1" />
-    <meta name="theme-color" content="#f6f6f6" media="(prefers-color-scheme: light)">
+    <meta name="theme-color" content="#fafafa" media="(prefers-color-scheme: light)">
     <meta name="theme-color" content="#121212" media="(prefers-color-scheme: dark)">
     <script type="module">
         if ('serviceWorker' in navigator) {

public/js/modules/graph.js

@@ -241,7 +241,7 @@ function getStylesheet() {
                 'label': !isTree ? 'data(displayWord)' : edgeLabel,
                 'color': (_ => prefersDark ? '#eee' : '#000'),
                 'font-size': isTree ? '12px' : '10px',
-                'text-background-color': (_ => prefersDark ? '#121212' : '#f6f6f6'),
+                'text-background-color': (_ => prefersDark ? '#121212' : '#fafafa'),
                 'text-background-opacity': '1',
                 'text-background-shape': 'round-rectangle',
                 'text-background-padding': '1px',