Fixes to Unleashing ETC post

[IstoraMandiri]

This PR makes some tweaks to the recent blog post by @TheCrowbill #1162

I understand that you may not have been aware of these particular details, so please don't worry. However, I have a proposed a few changes that I believe could be helpful.

• rename contributor to contributors to make avatar appear properly
• remove opinion tag, instead use disclaimer: opinion, see Reorganize tags #1121
• Convert gif to jpg, although gifs will render, gatsby can only resize/process png/jpegs, so should be used images that aren't animated
• Add reference to original medium blog at the bottom of the post
• Format the quote differently

Thank you for the post!

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[TheCrowbill]

Thank you, @IstoraMandiri. I did not know how to apply most of the style subtleties.

One thing I would like to comment on is the file formatting for the image.

For image processing, I used Adobe Elements. When preparing image files for use on a website, it supposedly analyzes the image then optimizes such things as compression level and resolution, and finally recommends a file format. I've noticed that 99% of the time it recommends .jpeg formatting. For a few images, however, it chooses a .gif format even though the image is not animated. This was one of those oddball images, apparently.