Fixed typo and added some fileendings which older versions generate

AltiumDesigner.gitignore

@@ -12,7 +12,9 @@ Project\ Outputs*
 # Misc files generated by altium
 debug.log
 Status\ Report.txt
-*PcbDoc..htm
+*.PcbDoc.htm
+*.SchDocPreview
+*.PcbDocPreview
 
 # Lock files sometimes left behind
 .~lock.*