Clarified *.tmc-files rule.

TwinCAT3.gitignore

@@ -8,6 +8,9 @@
 *.tclrs
 *.compiled-library
 *.compileinfo
+# Don't include the tmc-file rule if either of the following is true:
+#   1. You've got TwinCAT C++ projects, as the information in the TMC-file is created manually for the C++ projects (in that case, only (manually) ignore the tmc-files for the PLC projects)
+#   2. You've created a standalone PLC-project and added events to it, as these are stored in the TMC-file.
 *.tmc
 *.tmcRefac
 *.library