Update demo content for themes about hugobasicexample

[hanzei]

I looked for markdown explanations and found two:

• https://spec.commonmark.org/
• https://daringfireball.net/projects/markdown/syntax

I don`t know if we are allowed to use there text for this repository. So I ask them about the license. (See commonmark/commonmark-spec-web#12)

[onedrawingperday]

Due to enforcing this repo's contentDir with gohugoio/hugoThemes#547 in theme demos on the Hugo showcase, now several themes have missing content due to various reasons.

So I am assigning this issue to myself.

• I will be looking into overhauling the content directory of this repository and expanding it to accommodate themes that use Page Bundles and complex -but very popular- themes such as Academic.

• Also I will be addressing the concerns raised here and in #7 about outdated Hugo Documentation by removing it.

• Also I am in favor of displaying:

the basics of Markdown to show how elements of the website like headers, paragraphs, images and tables look with a certain theme

There will be some Pull Requests coming around the end of February.

ref: HugoBlox/hugo-blox-builder#898