Support symbols in text

I recently wanted an operation text to contain a pipe, which seems not to be possible at the moment.
The README says
> Symbols that should possibly not be used in the text: '=>' and '->' and ':>' and '|' and '@>'

I'd love to see some sort of escaping for these symbols, since ascii arrows and pipes are commonly used symbols.

I could imagine two possible ways of escaping: Either place a `\` in front of the symbol, or write the whole text in quotes and match the first and the last quote of a line:

```
op1=>operation: text \| with \-> symbols|flowstate
op2=>operation: "text | with -> symbols"|flowstate
```