textgen: Generate CREDIT screen.

This is one of the screens of text shown between demos in the demo
loop. Generate this from the contents of a static text file. I
originally wanted to generate this programatically from the CREDITS
file but there are too many contributors to fit them all on the page.

graphics/text/config.py

@@ -109,6 +109,8 @@ blue_graphics = {
 red_graphics = {
 	# Title for the HELP/HELP1 screen:
 	'helpttl': 'Help',
+	# Title for CREDIT
+	'freettl': 'Freedoom',
 
 	'm_ngame': 'New Game',
 	'm_option': 'Options',