Add problems URL again.

My last commit removed them for some reason...

lua/plugins/competitest.lua

@@ -18,6 +18,8 @@ return {
             end
         end,
         testcases_use_single_file = true,
+        evaluate_template_modifiers = true,
+        received_problems_prompt_path = false,
         compile_command = {
             c = { exec = "gcc", args = { "-Wall", "-g", "-DDEBUG", "-fsanitize=address,undefined", "-std=c++17", "$(FNAME)", "-o", "$(FNOEXT).out" } },
             cpp = { exec = "g++", args = { "-Wall", "-g",  "-DDEBUG", "-fsanitize=address,undefined", "-std=c++17", "$(FNAME)", "-o", "$(FNOEXT).out" } },

templates/template.c

@@ -1,3 +1,5 @@
+/* Problem URL: $(URL) */
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <math.h>

templates/template.cpp

@@ -1,3 +1,5 @@
+/* Problem URL: $(URL) */
+
 #include <bits/stdc++.h>
 
 using namespace std;