Update README to show cases where markup do is not required

[smpallen99]

With the new AST approach (removal of ETS), there are some new syntax allowed. Mainly, markup do is only required when more than one top level element is used (automatic string concat). We should provide some examples.

[romul]

I guess we could use examples without markup and then add a section with smth like

If you want generate several siblings elements without wrapping them in div, you could use markup:
examples