chore: add instructions for dependency installation

hello-world/readme.md

@@ -1,3 +1,9 @@
+* install dependencies on Debian Bullseye
+
+```
+sudo apt install libulfius-dev --no-install-recommends
+```
+
 * build
 
 ```

libjansson/main.c

@@ -116,7 +116,7 @@ int callback_get_hello (const struct _u_request * request, struct _u_response *
   json_decref(integer1);
   json_decref(integer2);
   size = json_array_size(array);
-  fprintf(stdout,"main() size: %ld\n", size);
+  fprintf(stdout,"main() size(array): %ld\n", size);
 
   ulfius_set_json_body_response(response, 200, array);
   json_decref(array);

libjansson/readme.md

@@ -1,3 +1,9 @@
+* install dependencies on Debian Bullseye
+
+```
+sudo apt install libulfius-dev --no-install-recommends
+```
+
 * build
 
 ```