Add mgp_result_reserve to C-API (#1236)

* docs

* docs

Author: imilinovic

pages/custom-query-modules/c/c-api.mdx

@@ -143,6 +143,7 @@ Memgraph in order to use them.
 | enum [mgp_error](#variable-mgp-error) | **[mgp_path_equal](#function-mgp-path-equal)**(struct mgp_path * p1, struct mgp_path * p2, int * result)<br />Result is non-zero if given paths are equal, otherwise 0.  |
 | enum [mgp_error](#variable-mgp-error) | **[mgp_result_set_error_msg](#function-mgp-result-set-error-msg)**(struct mgp_result * res, const char * error_msg)<br />Set the error as the result of the procedure.  |
 | enum [mgp_error](#variable-mgp-error) | **[mgp_result_new_record](#function-mgp-result-new-record)**(struct mgp_result * res, struct mgp_result_record ** result)<br />Create a new record for results.  |
+| enum [mgp_error](#variable-mgp-error) | **[mgp_result_reserve](#function-mgp-result-reserve)**(struct mgp_result * res, size_t n)<br />Reserves memory for `n` result records.  |
 | enum [mgp_error](#variable-mgp-error) | **[mgp_result_record_insert](#function-mgp-result-record-insert)**(struct mgp_result_record * record, const char * field_name, struct mgp_value * val)<br />Assign a value to a field in the given record.  |
 | void | **[mgp_properties_iterator_destroy](#function-mgp-properties-iterator-destroy)**(struct mgp_properties_iterator * it)<br />Free the memory used by a mgp_properties_iterator.  |
 | enum [mgp_error](#variable-mgp-error) | **[mgp_properties_iterator_get](#function-mgp-properties-iterator-get)**(struct mgp_properties_iterator * it, struct [mgp_property](#mgp_property) ** result)<br />Get the current property pointed to by the iterator.  |
@@ -1659,6 +1660,17 @@ Create a new record for results.
 
 The previously obtained mgp_result_record pointer is no longer valid, and you must not use it. Return MGP_ERROR_UNABLE_TO_ALLOCATE if unable to allocate a mgp_result_record.
 
+### mgp_result_reserve [#function-mgp-result-reserve]
+```cpp
+enum mgp_error mgp_result_reserve(
+    struct mgp_result * res,
+    size_t n
+)
+```
+
+Reserves memory for `n` result records.
+
+Returns MGP_ERROR_UNABLE_TO_ALLOCATE if there's no memory for allocating the records.
 
 ### mgp_result_record_insert [#function-mgp-result-record-insert]
 ```cpp
@@ -4040,6 +4052,8 @@ enum mgp_error mgp_result_set_error_msg(struct mgp_result *res, const char *erro
 
 enum mgp_error mgp_result_new_record(struct mgp_result *res, struct mgp_result_record **result);
 
+enum mgp_error mgp_result_reserve(struct mgp_result *res, size_t n);
+
 enum mgp_error mgp_result_record_insert(struct mgp_result_record *record, const char *field_name,
                                         struct mgp_value *val);