chore: fix styles on typedoc generated API reference pages (#2148)

Fixes `font-size`-related rendering bugs. Follows
https://crawlee.dev/js/api as the original source of visual style.

|before|after|
|---|---|
|<img width="1460" height="1211" alt="image"
src="https://github.com/user-attachments/assets/48267e7d-c32d-439e-b455-c1c5f4f6a203"
/>| <img width="1460" height="1211" alt="image"
src="https://github.com/user-attachments/assets/7cc9d0fd-f4ff-4b6c-a0ee-ebcd0d1ae027"
/> |

Closes apify/apify-sdk-js#531

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Adjusts fonts, heading sizes, and TypeDoc spacing; adds `Lota
Grotesque` font for headings to fix API reference typography.
> 
> - **CSS (apify-docs-theme/src/theme/custom.css)**:
> - **Typography**: Set `--ifm-heading-font-family` to `Lota Grotesque`;
added `@font-face` for `Lota Grotesque`.
> - **TypeDoc layout**: Introduced `--tsd-spacing-*` variables; tuned
`.tsd-flag-group` margin and `.tsd-comment` spacing.
> - **Headings**: Added explicit sizes for `.apiItemContainer h2–h5`;
refined Markdown heading size variables.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
1403943. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: barjin

apify-docs-theme/src/theme/custom.css

@@ -126,12 +126,15 @@ html[data-theme='dark'] {
 
 :root {
     /* use default system font based on https://devhints.io/css-system-font-stack */
-    --ifm-font-family-base: -apple-system, BlinkMacSystemFont, 'Segoe UI',
-        'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans',
-        'Helvetica Neue', sans-serif;
-    --ifm-heading-font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI',
-        'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans',
-        'Helvetica Neue', sans-serif;
+    --ifm-font-family-base:
+        -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
+        'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
+        sans-serif;
+    --ifm-heading-font-family: 'Lota Grotesque', sans-serif;
+    --tsd-spacing-vertical: 1.2rem !important;
+    --tsd-spacing-horizontal: 1.6rem !important;
+    --ifm-list-item-margin: 0.4rem !important;
+    --ifm-list-left-padding: 3.2rem !important;
     --ifm-font-weight-semibold: 600;
     --ifm-font-color-base: #242736;
 
@@ -286,6 +289,34 @@ html[data-theme='dark'] {
     --button-gradient: linear-gradient(180deg, rgba(255, 255, 255, 0.3) 0%, rgba(255, 255, 255, 0) 100%);
 }
 
+@font-face {
+    font-family: 'Lota Grotesque';
+    src:
+        url('/font/lota.woff2') format('woff2'),
+        url('/font/lota.woff') format('woff');
+    font-weight: 600;
+}
+
+.apiItemContainer h2 {
+    font-size: 2.4rem;
+}
+
+.apiItemContainer h3 {
+    font-size: 2rem;
+}
+
+.apiItemContainer h4 {
+    font-size: 1.6rem;
+}
+
+.apiItemContainer h5 {
+    font-size: 1.4rem;
+}
+
+.tsd-comment {
+    margin-bottom: var(--tsd-spacing-vertical);
+}
+
 .markdown h1,
 .markdown h2,
 .markdown h3,
@@ -621,7 +652,7 @@ article .card h2 {
 }
 
 .tsd-panel-header .tsd-flag-group {
-    margin-right: .5rem;
+    margin-right: .8rem;
     margin-left: .5rem;
 }