addition: Added basic header and structure

src/arraylist.c

@@ -0,0 +1,34 @@
+#include "arraylist.h"
+#include <stdbool.h>
+#include <stdlib.h>
+
+ArrayListResult arraylist_init(size_t capacity, size_t elem_size) {
+    if (capacity == 0) {
+        return (ArrayListResult) {
+            .is_valid = false,
+            .err = ARRLIST_INVALID_CAPACITY};
+    }
+
+    if (elem_size == 0) {
+        return (ArrayListResult) {
+            .is_valid = false,
+            .err = ARRLIST_INVALID_ELEM_SIZE,
+        };
+    }
+
+    ArrayList arr = {
+        .data = malloc(capacity * elem_size),
+        .capacity = capacity,
+        .elem_size = elem_size,
+        .len = 0
+    };
+
+    if (arr.data == NULL) {
+        return (ArrayListResult) {
+            .is_valid = false,
+            .err = ARRLIST_BAD_ALLOC,
+        };
+    }
+
+    return (ArrayListResult) {.is_valid = true, .array = arr};
+}