feat(CodeBlock): add line wrapping to codeblock [wip]

[d3m1d0v]

Changes in CodeBlock:

• Text wrapping is disabled by default.
• Floating toolbar for code block has been redesigned:
  • Move PlainText to first position in the language select list.
  • Replace the "line numbers" checkbox with a toggle button
  • Add a copy button
  • Change the remove button theme to danger
• Add button to the floating toolbar to toggle text wrapping - it will only affect the current code block and only during current editing session for current user

Toolbar:

• add danger theme to single button

Also added a new example story where you can configure a code block.

[gravity-ui]

[gravity-ui]

[makhnatkin]

@d3m1d0v I suggest using negative margin for the first element and padding for the container

.yfm-line-number {
    margin-left: -2rem;
}
.hljs > div {
    padding-left: 2rem
}