Local project checks and contribution templates: make check, dependency-free C/python tests, issue forms + blank issues, CONTRIBUTING (#20)

* Add lightweight project checks and templates

* Ignore generated test binaries

* Keep project checks local

c/tests/test_st.c

@@ -0,0 +1,26 @@
+#include <math.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include "../st.h"
+
+#define CHECK(condition) do { \
+    if (!(condition)) { \
+        fprintf(stderr, "%s:%d: check failed: %s\n", __FILE__, __LINE__, #condition); \
+        return 1; \
+    } \
+} while (0)
+
+int main(void) {
+    CHECK(bf16_to_f32(0x3f80) == 1.0f);
+    CHECK(bf16_to_f32(0xc020) == -2.5f);
+    CHECK(f16_to_f32(0x3c00) == 1.0f);
+    CHECK(f16_to_f32(0xc100) == -2.5f);
+    CHECK(f16_to_f32(0x0001) > 0.0f);
+    CHECK(isinf(f16_to_f32(0x7c00)));
+    CHECK(st_hash("tensor.weight") == st_hash("tensor.weight"));
+    CHECK(st_hash("tensor.weight") != st_hash("tensor.bias"));
+
+    puts("safetensors primitive tests: ok");
+    return 0;
+}