feat(lsm): added trie search

lsm/include/lsm/str.h

@@ -34,6 +34,15 @@ void lsm_str_init_prealloc(lsm_str *str, char *s);
  */
 lsm_error lsm_str_init(lsm_str **ptr, char *s);
 
+/**
+ * Same as lsm_str_init, except it copies the original string instead of taking
+ * over ownership, leaving the original string untouched.
+ *
+ * @param ptr pointer to store newly allocated pointer
+ * @param s string to copy into lsm string
+ */
+lsm_error lsm_str_init_copy(lsm_str **ptr, char *s);
+
 /**
  * Deallocate the existing internal string if needed and replace the lsm_str
  * with a string of length 0, wiping its contents.