Add alt-text tags to post-chart build pages

[o-fish-wildaid]

Add alt-text tags to the troubleshooting page:

Page exists at: https://wildaid.github.io/charts/2020/06/14/TroubleshootingCharts.html In the code at: _posts/build_charts/2020-06-14-TroubleshootingCharts.md

A brief guide to alt-text tags can be found in our style guide at https://wildaid.github.io/style/2020/10/02/Alt-Text.html

[jessicasalbert]

Hey, I've read the guidelines and would love to work on this issue if you could to assign it to me. Thanks!

[Sheeri]

Hello, thanks for offering to work on this! I have assigned it to you @jessicasalbert