Favour CDN image URLs over GitHub
Following on from PR #344, further adjustments to improve README and always use CDN URLs for downloading icon images.
Specifying a target URL/anchor helps preserve image file names on hover and when saving, instead of defaulting to meaningless https://camo.githubusercontent.com/<very long string>.png format.
In both Firefox and Chrome, the 'Save link as' context menu option should now default to saving a PNG matching the image file name.
Note: pointing the target URL to the underlying (non-raw) image repository location on GitHub would lead to Chrome saving links as HTML files, ruling this out as an alternative approach
Some other slight tweaks to simplify shell download examples.
Just giving a quick update on this.
This PR will be integrated once the #353 PR is merged. Currently, it will break the branch because JSDelivr doesn't support branch detection.