fix some type errors

lib/templates.ts

@@ -1,8 +1,8 @@
-function convertLineBreaks(string) {
-  return string.replace(/\n/g, '\\\\')
+function convertLineBreaks(lines: string) {
+  return lines.replace(/\n/g, '\\\\')
 }
 
-export function brief(options) {
+export function brief(options: Record<string, string>) {
   const {
     template = 'brief-fam',
     subject = '',