Add stupid README

README.md

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+# FitsPHP - A dumb FITS image library for PHP
+
+FitsPHP (or `fits-php`) is a dumb and crappy "library" to somehow interact with the FITS image format used in astronomy.  
+The library tries to implement a reasonable subset of the [FITS standard](https://fits.gsfc.nasa.gov/fits_standard.html). Of course, it all depends on the definition of 'reasonable'...
+
+## Usage
+
+Add the package with Composer:
+
+```
+composer require dumbastro/fits-php
+```
+
+then use classes from the `Dumbastro\FitsPhp` namespace.
+
+### Examples
+
+Retrieve the image blob for a given FITS file then do something with the bytes:
+
+```php
+<?php
+
+declare(strict_types=1);
+
+use Dumbastro\FitsPhp\Fits;
+use Dumbastro\FitsPhp\FitsHeader;
+use Dumbastro\FitsPhp\ImageBlob;
+
+$fits = new Fits('bubble_nebula.fit');
+$blob = new ImageBlob($header, $fits->imageBlob);
+
+foreach ($blob->dataBytes() as $byte) {
+    // Do something useful...
+}
+```
+
+The method `ImageBlob::dataBytes` returns a `Generator`.
+
+