- Get familar with jison
- git graph requires a blank line at the end. why?
- Create a desktop client
- Flowchart `interpolate` is useless because there is no rendering code using it
- Each type of diagram should have its own set of CSS.
- Support customization of gantt diagram xAxis format
    - https://github.com/d3/d3-time-format#api-reference
    - https://bl.ocks.org/wboykinm/34627426d84f3242e0e6ecb2339e9065
    - Some one created a great PR: https://github.com/knsv/mermaid/pull/624