Update .gitattributes export-ignore

- remove non-existent entries
- add new ones not necessary for installations

Since the diff is a bit hard to read as I also sorted things alphabetically:

removed:
- /.scrutinizer.yml
- /.travis.yml

added:
- /.editorconfig
- /.github
- /.php_cs.dist

Author: mfn

.gitattributes

@@ -2,13 +2,14 @@
 # https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html
 
 # Ignore all test and documentation with "export-ignore".
+/.editorconfig     export-ignore
 /.gitattributes     export-ignore
+/.github            export-ignore
 /.gitignore         export-ignore
-/.travis.yml        export-ignore
+/.php_cs.dist       export-ignore
+/example            export-ignore
 /phpunit.xml.dist   export-ignore
-/.scrutinizer.yml   export-ignore
 /tests              export-ignore
-/example            export-ignore
 
 # All test snapshots and text stubs must have LF line endings
 tests/**/__snapshots__/**   text eol=lf