frost: initialize project

This commit adds the foundational configuration and building scripts
and an initial structure for the project.

include/secp256k1_frost.h

@@ -0,0 +1,22 @@
+#ifndef SECP256K1_FROST_H
+#define SECP256K1_FROST_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+
+/** This code is currently a work in progress. It's not secure nor stable.
+ * IT IS EXTREMELY DANGEROUS AND RECKLESS TO USE THIS MODULE IN PRODUCTION!
+ *
+ * This module implements a variant of Flexible Round-Optimized Schnorr
+ * Threshold Signatures (FROST) by Chelsea Komlo and Ian Goldberg
+ * (https://crysp.uwaterloo.ca/software/frost/).
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif