patch 8.1.2219: no autocommand for open window with terminal

Problem:    No autocommand for open window with terminal.
Solution:   Add TerminalWinOpen. (Christian Brabandt)
diff --git a/src/vim.h b/src/vim.h
index 43eecf0..917dbfa 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1341,6 +1341,7 @@
     EVENT_TABNEW,		// when entering a new tab page
     EVENT_TERMCHANGED,		// after changing 'term'
     EVENT_TERMINALOPEN,		// after a terminal buffer was created
+    EVENT_TERMINALWINOPEN,	// after a terminal buffer was created and entering its window
     EVENT_TERMRESPONSE,		// after setting "v:termresponse"
     EVENT_TEXTCHANGED,		// text was modified not in Insert mode
     EVENT_TEXTCHANGEDI,         // text was modified in Insert mode