Add boolean syntax guide

[m-mujica]

@matthewp I made some changes based on your feedback, also:

• Renamed the page to "Boolean Conditional Guide"
• Renamed the custom element to MyElement (not BitProduct)
• Changed the folder name to boolean-demo instead of bitovi-grid

Something I noticed is, the extension supports negation using ~ before the condition module, the guide doesn't mention it neither does the README file. Should I add a brief mention in the README file or something like

in the guide itself? I think in the README makes more sense.

[matthewp]

I think you could add a blockquote mention about it, and link to the docs about it (the readme or wherever that lives).

[m-mujica]

👍 👎 ?

[m-mujica]

I'm going to merge this one 💥