docs: add documentation for ggml_trunc and ggml_trunc_inplace in ggml.h

Author: safranowith

ggml/include/ggml.h

@@ -1177,6 +1177,12 @@ extern "C" {
             struct ggml_context * ctx,
             struct ggml_tensor  * a);
 
+     /**
+     * Truncates the fractional part of each element in the tensor (towards zero).
+     * For example: trunc(3.7) = 3.0, trunc(-2.9) = -2.0
+     * Similar to std::trunc in C/C++.
+     */      
+
     GGML_API struct ggml_tensor * ggml_trunc(
             struct ggml_context * ctx,
             struct ggml_tensor  * a);