spdx-license-diff - useful browser addon/extension for licence lookups and checks

Hi folks,

When packaging or adopting a package, it can be useful to lookup the official 
SPDX licence id to add after cygport `LICENSE=`, or check if the cygport 
official SPDX licence id `LICENSE=` is correct or needs updated.

Some licences have subtle differences from each other, and variations that are 
difficult to distinguish, for those who do not have an eidetic memory for 
licence texts, and a mental facility to easily perform such comparisons.

The GPL-3.0 licensed SPDX License Diff browser addon/extension for Chrome, Edge, 
Firefox, and Opera based browsers allows you to lookup and check package licence 
texts easily and quickly:

	https://github.com/spdx/spdx-license-diff/releases

It allows you to clear and update the SPDX License List data, set an interval 
for checking for List updates, other checking criteria, display and highlight 
colours.

After installing and enabling the browser addon/extension, enable display of its 
icon in your browser window, access your package licence text in a browser 
window, for example, with a file:// URI, or from a web repo, select the licence 
text to be checked, and click the addon/extension icon to perform a (local 
browser) lookup and comparison.

SPDX License Diff will highlight in different colours matching mandatory and 
optional licence text and unmatched extraneous text, and display the highest 
probability matching SPDX licence id.

Where GNU or other licences offer -only or -or-later variations, you will have 
to read other package docs to distinguish those terms, as those are not part of 
the GNU licence texts.

Hope others find this SPDX License Diff browser addon/extension as useful as I 
have over the last few years, and don't have any objections to my belated 
decision to mention it to maintainers and packagers.

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retrancher  but when there is no more to cut
                                 -- Antoine de Saint-Exupéry