Whitespace improvements (retry)

[kmk3]

$ git log --reverse --pretty='* %s' -s master..HEAD
* Add .gitattributes
* Fix whitespace with git stripspace
* .editorconfig: enable trim trailing ws / insert final newline
* .editorconfig: define consistent charset and eol

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(Re-attempt of #143 without squashing on merge)

[xuhdev]

Done!