Issue 10 ci add support for code spelling checks (#231)

* added make targets spell and codespell for spelling checks

* fix spelling errors detected by codespell

* added codespell to github workflow

Co-authored-by: Steve Karg <skarg@users.sourceforge.net>

src/bacnet/basic/object/schedule.c

@@ -74,7 +74,7 @@ void Schedule_Init(void)
     SCHEDULE_DESCR *psched = &Schedule_Descr[0];
 
     for (i = 0; i < MAX_SCHEDULES; i++, psched++) {
-        /* whole year, change as neccessary */
+        /* whole year, change as necessary */
         psched->Start_Date.year = 0xFF;
         psched->Start_Date.month = 1;
         psched->Start_Date.day = 1;