Keep modification time the same as the original file

[avdv]

When using the gzip_static on` directive of nginx, the manual says:

The files can be compressed using the gzip command, or any other compatible one. It is recommended that the modification date and time of original and compressed files be the same.

[caljess599]

I'm also trying to use this plugin in combination with nginx's gzip_static directive. Modern versions of nginx don't require the uncompressed files to be present in addition to the compressed ones, but what I am finding is that nginx seems to expect a gzipped file to have the .gz extension. So what I'd be looking for is a version of the keep setting that allows compressed files to be renamed rather than keeping the original alongside the compressed version.

[lukemelia]

@avdv @caljess599 These both seems like reasonable additions to this plugin. I'm happy to review a PR for one or both of them.

[avdv]

nginx seems to expect a gzipped file to have the .gz extension. So what I'd be looking for is a version of the keep setting that allows compressed files to be renamed rather than keeping the original alongside the compressed version.

I was really confused by this statement. Now I learned that keep = false does not simply remove the original file, but moves the gzipped file into its place. I would have never expected that! 🤯

@lukemelia FYI, I have updated PR #33 making the CI pass