string: new string library

Strings are simply byte vectors.  We want a separate type so when
tagging/untagging we can have some level of type separation.

src/string.c

@@ -0,0 +1,44 @@
+/* string.c: String library implementation
+ * Created: 2026-03-05
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#include <string.h>
+
+#include <alisp/string.h>
+
+str_t string_make(sv_t sv)
+{
+  str_t string = {0};
+  if (sv.size)
+  {
+    vec_init(&string.data, sv.size);
+    if (sv.data)
+    {
+      memcpy(vec_data(&string.data), sv.data, sv.size);
+    }
+  }
+  return string;
+}
+
+sv_t string_sv(str_t *str)
+{
+  if (!str)
+    return SV(NULL, 0);
+  return SV((char *)vec_data(&str->data), str->data.size);
+}
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */