Support symbols in text

[lkstz]

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

[adrai]

Feel free to submit a PR for the way that suits better for you.