Show Markdown effects on text in the UI

[HusniMuhammad]

Add text formating with options like
Bold
Italic
Underline
Strike-though

Text coloring (optional)

Please add if you can

Thanks :)

[CampelloManuel]

It is possible.
For example, text written **like this** could be displayed in bold in the app.
It would be only a graphical change, as the note would still be saved in plain text.

Implementation roadmap:

• decide wether https://github.com/noties/Markwon or https://github.com/yydcdut/RxMarkdown should be used
• when the text of the note is read and set in the TextView, treat it as markdown and convert it to Spannable, so that it can be set as formatted Text on the TextView
• add checks to fallback to plaintext in case of crashes or long note texts
• only render the first N lines of text as markdown, with N = the number of rows, from the app settings
• test (with multiple app settings) and publish