Fix#4521. Reader/Csv (which can be invoked by IOFactory::read), checks the mimetype of files if they don't have a csv/tsv extension. It allows empty files, whose mimetype was set to `inode/x-empty` for Php5.3.11 through Php7.3.33 (except for 5.4.0). For 5.3.1-5.3.10, 5.4.0, and 7.4.0+, the mimetype is `application/x-empty`. Reader/Csv recognizes the `inode` version but not the `application` version, which this PR adds.
The person who issued the report also noted that, for a file consisting of cr-lf, Php8.1.* and Php8.2.* report the mimetype as `application/octet-stream`, whereas all other releases report it as `text/plain`. The behavior of Php8.1/2 seems to be a bug, and I cannot possibly guess all the conditions that might lead to that bug. So I will not fix that problem. Anyone who is adversely affected by it can either add a `csv` extension to the filename, or upgrade to Php8.3+, or pre-process the file (e.g. to make it truly empty) before passing it to PhpSpreadsheet. A test case to document the problem is added for documentary purposes; the test will be skipped for Php8.1/2, but run for all other releases.
oleibman