[Client] Add transitions for theme switcher button and footer links

The following are also included in this commit:
- add missing swap property for Titan One font;
- move links decoration and visited properties into a specific class, link


Co-authored-by: Cazals Mathias <mathiascazals@users.noreply.github.com>

truthseeker/static/css/game_ui.css

@@ -1,6 +1,6 @@
 /* Custom fonts */
 @font-face {
-    font-family: 'Spicy Rice';
+    font-family: "Spicy Rice";
     font-style: normal;
     font-weight: 400;
     font-display: swap;
@@ -9,9 +9,10 @@
 }
 
 @font-face {
-    font-family: 'Titan One';
+    font-family: "Titan One";
     font-style: normal;
     font-weight: 400;
+    font-display: swap;
     src: url("../fonts/titan_one_v13/titan_one_v13.woff2") format('woff2'), url("../fonts/titan_one_v13/titan_one_v13.woff") format('woff'), url("../fonts/titan_one_v13/titan_one_v13.ttf") format('truetype');
     unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+2000-206F, U+2074, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
 }
@@ -46,6 +47,15 @@ body {
     display: none;
 }
 
+/* Links */
+.link {
+    text-decoration: none;
+}
+
+.link:visited {
+    color: unset;
+}
+
 /* Footer */
 .footer_link {
     color: white;
@@ -53,11 +63,11 @@ body {
     font-size: 1em;
     font-weight: bold;
     margin: 0.5em;
-    text-decoration: none;
+    transition: color 0.25s;
 }
 
-.footer_link:visited {
-    color: unset;
+.footer_link:hover {
+    color: #939393;
 }
 
 .footer_links {
@@ -121,4 +131,12 @@ body {
     height: 100vh;
     width: 100vw;
     z-index: 1;
-}
+}
+
+.theme_switcher_btn {
+    transition: fill 0.5s;
+}
+
+.theme_switcher_btn:hover {
+   fill: #939393;
+}