Add link to the online docs to kotlinc's help

#KT-35111 Fixed

compiler/cli/src/org/jetbrains/kotlin/cli/common/Usage.java

@@ -61,6 +61,11 @@ public class Usage {
             appendln(sb, BAT_DELIMITER_CHARACTERS_NOTE);
         }
 
+        if (!extraHelp && tool instanceof CLICompiler<?>) {
+            appendln(sb, "");
+            appendln(sb, "For details, see https://kotl.in/cli");
+        }
+
         return sb.toString();
     }
 

compiler/testData/cli/js/jsHelp.out

@@ -33,4 +33,6 @@ where possible options include:
   -verbose                   Enable verbose logging output
   -version                   Display compiler version
   @<argfile>                 Read compiler arguments and file paths from the given file
+
+For details, see https://kotl.in/cli
 OK

compiler/testData/cli/jvm/help.out

@@ -31,4 +31,6 @@ where possible options include:
   -verbose                   Enable verbose logging output
   -version                   Display compiler version
   @<argfile>                 Read compiler arguments and file paths from the given file
+
+For details, see https://kotl.in/cli
 OK