docs: use local Noto Sans font

Co-authored-by: Junie <junie@jetbrains.com>

docs/assets/css/custom.css

@@ -0,0 +1,39 @@
+@font-face {
+  font-family: 'Noto Sans';
+  font-style: normal;
+  font-weight: 400;
+  font-display: swap;
+  src: url('../fonts/noto-sans-v42-latin-regular.woff2') format('woff2');
+}
+
+@font-face {
+  font-family: 'Noto Sans';
+  font-style: italic;
+  font-weight: 400;
+  font-display: swap;
+  src: url('../fonts/noto-sans-v42-latin-italic.woff2') format('woff2');
+}
+
+@font-face {
+  font-family: 'Noto Sans';
+  font-style: normal;
+  font-weight: 700;
+  font-display: swap;
+  src: url('../fonts/noto-sans-v42-latin-700.woff2') format('woff2');
+}
+
+@font-face {
+  font-family: 'Noto Sans';
+  font-style: italic;
+  font-weight: 700;
+  font-display: swap;
+  src: url('../fonts/noto-sans-v42-latin-700italic.woff2') format('woff2');
+}
+
+:root {
+  --hx-default-font-family: "Noto Sans", ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
+}
+
+.content {
+  font-family: var(--hx-default-font-family);
+}