Stackedit: flowchart renders as code

[mordrax]

Firstly, this is a nice app, thanks for creating it.

My issue is that the example flowchart doesn't render when I copy paste it into my document. It also doesn't work when I create a new document and paste it there.

```flow
st=>start: Start
e=>end
op=>operation: My Operation
cond=>condition: Yes or No?

st->op->cond
cond(yes)->e
cond(no)->op
```.

The period at the end is because I don't know how to escape '```' to demonstrate I'm just copying the flowchart.

Version 5.7.1

[benweet]

StackEdit v5 now uses the Mermaid syntax for charts and diagrams.

Example:

```mermaid
sequenceDiagram
Alice ->> Bob: Hello Bob, how are you?
Bob-->>John: How about you John?
Bob--x Alice: I am good thanks!
Bob-x John: I am good thanks!
Note right of John: Bob thinks a long<br/>long time, so long<br/>that the text does<br/>not fit on a row.

Bob-->Alice: Checking with John...
Alice->John: Yes... John, how are you?
```