✨ (theme) Custom font option (#1268)

Closes #1249

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- Introduced components for customizing fonts, including Google and
custom font options.
- Enhanced theme customization by simplifying theme objects and adding
new font customization options.
- Implemented dynamic font injection for web pages based on
user-selected font configurations.

- **Bug Fixes**
- Fixed a condition in theme template card rendering to correctly check
avatar enablement.
- Corrected font property handling across various components to support
both string and object types.

- **Refactor**
	- Updated option properties in RadioButtons component to be readonly.
- Simplified logic for setting CSS variables for fonts, including checks
for font types and existence.

- **Documentation**
- Added constants and schemas for supporting new font types in theme
customization.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/builder/src/components/inputs/RadioButtons.tsx

@@ -10,7 +10,7 @@ import {
 import { ReactNode } from 'react'
 
 type Props<T extends string> = {
-  options: (T | { value: T; label: ReactNode })[]
+  options: readonly (T | { value: T; label: ReactNode })[]
   value?: T
   defaultValue?: T
   direction?: 'row' | 'column'