docs: what is

README.md

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 # MimeTypes
 This is a comprehensive compilation of MIME types that is periodically updated through the following projects: [Apache](https://github.com/apache/httpd/blob/trunk/docs/conf/mime.types), [NGINX](https://github.com/nginx/nginx/blob/master/conf/mime.types), [IANA](https://www.iana.org/assignments/media-types/media-types.xhtml) and [Debian](https://salsa.debian.org/debian/media-types/-/blob/master/mime.types)
+
+
+## What is
+A file's extension has no meaning on the web. In order for the client to interpret the document correctly, the MIME type must be sent in the Content-Type header.