Add pagination to search results.

Move to shared definition of json requests between client/server.

shared/src/lib.rs

@@ -0,0 +1,11 @@
+use notmuch::SearchSummary;
+use serde::{Deserialize, Serialize};
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct SearchResult {
+    pub summary: SearchSummary,
+    pub query: String,
+    pub page: usize,
+    pub results_per_page: usize,
+    pub total: usize,
+}