Add custom theme

Based on my website's current theme

assets/theme.css

@@ -0,0 +1,66 @@
+:root {
+  --body-background-color: #004a99;
+  --body-text-color: #cce6ff;
+  --card-background-color: #004a99;
+  --nav-background-color: #004a99;
+  --nav-border-bottom-color: #80c1ff;
+  --nav-current-border-bottom-color: #1abc9c;
+  --card-border-color: #80c1ff;
+  --down-border-left-color: #eb3b5a;
+  --down-background-color: #6b1020;
+  --degraded-border-left-color: #f7b731;
+  --up-border-left-color: #20bf6b;
+  --tag-color: #004a99;
+  --tag-up-background-color: #20bf6b;
+  --tag-down-background-color: #eb3b5a;
+  --tag-degraded-background-color: #f7b731;
+  --change-background-color: #f7b731;
+  --error-button-border-color: #1a46ad;
+  --error-button-background-color: #3867d6;
+  --error-button-color: #ffffff;
+  --submit-button-border-color: #1a46ad;
+  --submit-button-background-color: #3867d6;
+  --submit-button-color: #ffffff;
+  --graph-opacity: 1;
+  --graph-filter: none;
+}
+
+body {
+  background-color: var(--body-background-color);
+}
+
+body::before,
+body::after {
+  background: linear-gradient(to bottom, var(--body-background-color), var(--body-background-color)00);
+}
+
+h1, h2, h3, h4, h5, h6, p, sub, li, a {
+  font-family: 'Quicksand', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
+  color: var(--body-text-color);
+}
+
+figcaption {
+  text-align: center;
+  color: var(--body-text-color)81;
+}
+
+hr {
+  border: 5px solid var(--nav-border-bottom-color);
+  box-shadow: 0 5px 10px #00000015;
+}
+
+a:link {
+  color: #9ec2e6;
+}
+
+a:visited {
+  color: #90b2d4;
+}
+
+a:hover {
+  color: #a8cef5;
+}
+
+a:active {
+  color: #a7ccf1;
+}