feat: Add Credits & Attribution page

- add credits.njk
- add credits.css
- add tooltips.js
- add link in footer

src/styles/credits.css

@@ -0,0 +1,49 @@
+/* CSS Style Rules for "Credits & Attributions" */
+.credits-list {
+    list-style: none;
+    margin: 0;
+    padding: 0;
+}
+
+.credit {
+    display: flex;           /* thumb + text side by side */
+    align-items: flex-start;
+    gap: 0.5rem;             /* spacing between thumb and text */
+    margin-bottom: 1rem;
+}
+
+.thumb {
+  flex: 0 0 auto;          /* don’t stretch */
+}
+
+.thumb-inline {
+    display: block;          /* visible by default (no JS) */
+    max-width: 40px;         /* fallback size (from HTML attrs) */
+    height: auto;
+}
+
+.meta {
+    flex: 1 1 auto;
+    min-width: 0;            /* ensures text can wrap inside flexbox */
+    word-wrap: break-word;
+}
+
+.meta p {
+    margin: 0.25rem 0;
+}
+
+.meta .small {
+    font-size: 0.875rem;
+    color: #555;
+}
+
+.thumb-tooltip { /* background image is handled by JS */
+    position: absolute;
+    display: none;
+    background-repeat: no-repeat;
+    background-size: contain;   /* fit full image */
+    background-position: center;
+    border: 1px solid #ccc;
+    box-shadow: 0 4px 8px rgba(0,0,0,0.15);
+    z-index: 9999;
+}