bug #864 Remove development files from releases (phansys)

This PR was submitted for the master branch but it was merged into the 2.x branch instead.

Discussion
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Remove development files from releases

Environment specific files were also removed from `.gitattributes`. They should be [globally ignored](https://docs.github.com/es/github/getting-started-with-github/ignoring-files#configuring-ignored-files-for-all-repositories-on-your-computer) in the environment they exist.

Commits
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5988bb8 Remove development files from releases

.gitattributes

@@ -0,0 +1,6 @@
+.* export-ignore
+*.md export-ignore
+Resources/doc export-ignore
+Tests export-ignore
+phpunit.xml.dist export-ignore
+phpstan.neon export-ignore

.gitignore

@@ -2,6 +2,4 @@ phpunit.xml
 build
 vendor
 composer.lock
-composer.phar
-.idea
 .phpunit.result.cache