Add basic SQLite storage backend

scripts/policy/frameworks/storage/backend/sqlite/__load__.zeek

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+@load ./main.zeek

scripts/policy/frameworks/storage/backend/sqlite/main.zeek

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+##! SQLite storage backend support
+
+@load base/frameworks/storage/main
+
+module Storage::Backend::SQLite;
+
+export {
+	## Options record for the built-in SQLite backend.
+	type Options: record {
+		## Path to the database file on disk. Setting this to ":memory:"
+		## will tell SQLite to use an in-memory database. Relative paths
+		## will be opened relative to the directory where Zeek was
+		## started from. Zeek will not create intermediate directories
+		## if they do not already exist. See
+		## https://www.sqlite.org/c3ref/open.html for more rules on
+		## paths that can be passed here.
+		database_path: string;
+
+		## Name of the table used for storing data.
+		table_name: string;
+	};
+}