feat: implement SigVariant (#7)

README.md

@@ -1,7 +1,30 @@
 # blst-z
 Zig wrapper for [supranational/blst](https://github.com/supranational/blst) native bindings, a highly performant BLS12-381 signature library.
 
-# How to build
+## Installation
 - clone blst to root: `git clone --recurse-submodules https://github.com/supranational/blst.git`
-- `zig build`
-- locate `zig-out/lib/libblst-z.dylib` (could be diffrerent name in other OSs) and continue the test below
+- `zig build test`
+
+## Usage
+The below shows how to use min_pk namespace
+
+```zig
+pub const min_pk = @import("blst").min_pk;
+const SecretKey = min_pk.SecretKey;
+const ikm: [32]u8 = [_]u8{
+    0x93, 0xad, 0x7e, 0x65, 0xde, 0xad, 0x05, 0x2a, 0x08, 0x3a,
+    0x91, 0x0c, 0x8b, 0x72, 0x85, 0x91, 0x46, 0x4c, 0xca, 0x56,
+    0x60, 0x5b, 0xb0, 0x56, 0xed, 0xfe, 0x2b, 0x60, 0xa6, 0x3c,
+    0x48, 0x99,
+};
+const sk = try SecretKey.keyGen(ikm[0..], null);
+const pk = sk.skToPk();
+
+const dst = "BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_NUL_";
+const msg = "hello foo";
+// aug is null
+const sig = sk.sign(msg[0..], dst[0..], null);
+
+// aug is null
+try sig.verify(true, msg[0..], dst[0..], null, &pk, true);
+```