add slide for gitignore

2019/2019-10-10_advancedGitTraining-SIU/slides/ignore.md

+# Ignore files
+
+In the file `.gitignore`, all untracked files that should be ignored by `git` are listed:
+```
+.DS_Store
+data
+*.csv
+```
+
+If you want to exclude certain files from this list:
+```
+!*.yml
+config/*.yml
+```
+This tracks changes in all yml file, but not in the `config` folder.
+
+Examples: www.gitignore.io
\ No newline at end of file

2019/2019-10-10_advancedGitTraining-SIU/slides/list.json

@@ -2,6 +2,7 @@
     { "filename": "index.md" },
     { "filename": "overview.md" },
     { "filename": "gettingStarted.md" },
+    { "filename": "ignore.md" },
     { "filename": "amend.md" },
     { "filename": "reset.md" },
     { "filename": "revert.md" },