feat(email-renderer): add global brand styling

packages/email-renderer/src/email.ts

@@ -71,8 +71,13 @@ export const emailKind = defineDocumentKind({
   urlSchemes: ["https", "mailto"],
 });
 
-const head = (document: BlockDocument, body: string, direction: "ltr" | "rtl") =>
-  `<!doctype html><html lang="${escapeHtml(document.meta.lang)}" dir="${direction}"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1"><meta name="x-apple-disable-message-reformatting"><meta name="color-scheme" content="light dark"><title>${escapeHtml(document.meta.subject)}</title><style>@media only screen and (max-width:620px){.wrn-email{width:100%!important}.wrn-columns{display:block!important}.wrn-column{display:block!important;width:100%!important}}</style></head><body style="margin:0;padding:0;">${document.meta.preheader ? `<div style="display:none;max-height:0;overflow:hidden;opacity:0;">${escapeHtml(document.meta.preheader)}</div>` : ""}${body}</body></html>`;
+const head = (document: BlockDocument, body: string, direction: "ltr" | "rtl") => {
+  const props = document.root.props as Record<string, unknown>;
+  const textColor = escapeHtml(props.textColor ?? "#111827");
+  const linkColor = escapeHtml(props.linkColor ?? "#2563eb");
+  const fontFamily = escapeHtml(props.fontFamily ?? "Arial, sans-serif");
+  return `<!doctype html><html lang="${escapeHtml(document.meta.lang)}" dir="${direction}"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1"><meta name="x-apple-disable-message-reformatting"><meta name="color-scheme" content="light dark"><title>${escapeHtml(document.meta.subject)}</title><style>a{color:${linkColor}}@media only screen and (max-width:620px){.wrn-email{width:100%!important}.wrn-columns{display:block!important}.wrn-column{display:block!important;width:100%!important}}</style></head><body style="margin:0;padding:0;color:${textColor};font-family:${fontFamily};">${document.meta.preheader ? `<div style="display:none;max-height:0;overflow:hidden;opacity:0;">${escapeHtml(document.meta.preheader)}</div>` : ""}${body}</body></html>`;
+};
 const ampHead = (document: BlockDocument, body: string, direction: "ltr" | "rtl") =>
   `<!doctype html><html amp4email data-css-strict lang="${escapeHtml(document.meta.lang)}" dir="${direction}"><head><meta charset="utf-8"><script async src="https://cdn.ampproject.org/v0.js"></script><style amp4email-boilerplate>body{visibility:hidden}</style><style amp-custom>.email-body{max-width:600px;width:100%}.section{padding:24px}.button{background:#2563eb;border-radius:6px;color:#fff;display:inline-block;font-weight:700;padding:12px 20px;text-decoration:none}.spacer{height:24px}</style></head><body>${body}</body></html>`;