General cleanup of whitespace, typos

[stevegrunwell]

This PR cleans up a few general items (each in their own commit):

1. Adds .vscode to the .gitignore file
2. Introduce an .editorconfig file, based on the PSR-12 coding standards
3. Go through each file and re-save, stripping trailing whitespace on lines and adding a trailing newline to files where these were missing
4. Finally, fix a few typos in the README file