Fix: make jerryx_module_resolve resolvers argument const (#1942)

The resolvers argument that is passed to jerryx_module_resolve() is
not mutated by the function. Therefore the argument should be const.
In the docs, a static const array is passed, but this currently does not
work w/o a cast. This patch fixes this.

JerryScript-DCO-1.0-Signed-off-by: Martijn The martijn.the@intel.com

docs/12.EXT-REFERENCE-MODULE.md

@@ -38,7 +38,7 @@ called.
 ```c
 jerry_value_t
 jerryx_module_resolve (const jerry_char_t *name,
-                       jerryx_module_resolver_t *resolvers_p,
+                       const jerryx_module_resolver_t *resolvers_p,
                        size_t resolver_count);
 ```
 
@@ -134,7 +134,7 @@ load_and_evaluate_js_file (const jerry_char_t *name, jerry_value_t *result)
 
 We can now load JavaScript files:
 ```c
-static const jerryx_module_resolver_t resolvers =
+static const jerryx_module_resolver_t resolvers[] =
 {
   /* Consult the JerryScript module resolver first, in case the requested module is a compiled-in JerryScript module. */
   jerryx_module_native_resolver,