Issue / Improve Dev Mode

[livacengiz]

It should be easy to use the development environment and enter content

Tasks

•  watch md files via nuxt or trigger prebuild after on save
• remove mermaid-cli and render on clientside with mermaid package
• revise current content about mermaid setup
  • remove any obsolete documentation
  • add a new simple content to show how to setup mermaid

Additional Tasks

• add install command to Makefile
• remove extractDiagrams.js in prebuild
• remove @mermaid-js/mermaid-cli in package.json after remove extractDiagrams in prebuild repo