add support for habit pinning (#105)

lib/types.ts

@@ -44,6 +44,7 @@ export type Habit = {
   completions: string[] // Array of UTC ISO date strings
   isTask?: boolean // mark the habit as a task
   archived?: boolean // mark the habit as archived
+  pinned?: boolean // mark the habit as pinned
   userIds?: UserId[]
 }
 
@@ -197,4 +198,4 @@ export type ParsedResultType = DateTime<true> | RRule | string | null // null if
 export interface ParsedFrequencyResult {
   message: string | null
   result: ParsedResultType
-}
+}