optionally disable jupyter generation

[johnnychen94]

Currently, the same script is executed three times, which is not efficient especially when it comes with a lot of demos:

• Documenter rendering
• assets(e.g., cover) generation
• jupyter notebook generation

This issue plans to add a new keyword "notebook" to optionally disable jupyter notebook generation. I have plans to disable the assets generation as well, but I need to play with it first as it is deeply involved with the DemoCards design.

The jupyter notebook feature is perhaps not as attractive as I originally thought when I wrote this package.

This configuration needs to

• be able to configure/override at all levels (page/section/card)
• propagate to all children items
• parent configuration has lower priority than its children configuration

As an example:

examples/
├── color_channels
│   ├── config.json
│   ├── color_separations_svd.jl
│   ├── indexed_image.jl
│   ├── rgb_grayscale.jl
│   └── rgb_hsv_thresholding.jl
├── config.json
├── index.md
└── visualization
    └── block_visualization.jl

• If we disable the execution in "examples/config.json", then all the Julia demos are disabled by default.
• If we again enable the execution for examples/color_channels/config.json, then all demos in this section are enabled. It has a higher priority than its parent page settings.
• Similarly, if we configure this in the julia script(e.g., rgb_grayscale.jl), then it has the highest priority.

keywords for these will be case insensitive full match:

• enable: "enable", "yes", "true"
• disabled: "disable", "no", "false"

---

Example

For page/section:

{
    "notebook": "no",
}

For card:

---
notebook: no
---