Ability to add footer to chart on the front-end

[IosifGabriel]

An enhancement to be able to add sources to the data of graphs (possible footer/header like in this screenshot -> http://prntscr.com/p24vpo )

However, there is a workaround with JS <<thanks @SilviuDinu>>(it modifies the horizontal axis description but if the description is needed, there is no solution) with the following code, trying JSON from google's API doesnt work in manual configuration.

<script type = "text/javascript"> var chartTitle = document.querySelectorAll(".visualizer-front svg g g text"); for (var i = 0; i < chartTitle.length; i = i + 1) { if (chartTitle[i].innerHTML === 'Source: Data Insight') { chartTitle[i].setAttribute('x', 120); } }; </script>

Refference -> https://secure.helpscout.net/conversation/942172660/200370?folderId=212385

[contactashish13]

@IosifGabriel @SilviuDinu this can be done by adding an element in the post content below the shortcode or by adding a block in gutenberg. This does not need any exotic changes to JS.

Will keep this on hold to see how many people require this.

[contactashish13]

Can use the description field added for #399 if this is required.