Improve the default `site.json` settings generated during init

[damithc]

Justification: It lowers the initial barrier to entry as any folder with .md files can be served as a MarkBind site. The 'quick start' can omit mentioning markbind init and site.json altogether.

If the site.json is missing, we can use defaults for all configuration options and consider all *.md and *.mbd files as pages.

[yamgent]

1. I feel that markbind init and site.json are pretty important concepts to teach the users upfront (since they form the core of MarkBind), and 'quick start' is the best place to do that.
2. markbind init is easy to run anywhere. init does not pollute the user's folder structure much, so its effect is easily reversible if authors only want to try it out. We can tell the author to run markbind init and add "glob": "*.md" in site.json if they wish to try it on an existing folder.

[damithc]

Yes, it may be better to run init sooner than later. I'm also OK to expose the user to site.json early but I'd rather the user doesn't need to start tinkering with site.json right away. In other words, the site.json we generate should be good enough to last for a while.

How about we do these changes to markbind init?

1. Don't overwrite index.md if it exists
2. Tweak site.json/pages to serve all .mbd and .md files
3. Tweak site.json/ignore to ignore git folder. and all .mbd files

[yamgent]

• Don't overwrite index.md if it exists

This is already the behavior actually. In fact, all files inside _markbind/ also follows the same behavior.

• Tweak site.json/pages to serve all .mbd and .md files
• Tweak site.json/ignore to ignore git folder. and all .mbd files

Seems like a reasonable plan, since ideally the initial site.json created by init should be the default settings themselves.

Having all .md and .mbd files included is a sane default: I would think that authors should only have to worry about site.json when they require some additional setup, such as overriding the page title, rather than when they merely want to include a new .md file (in our current version, fiddling with site.json is a must once you have a file that is not index.md).

[damithc]

Upping the priority as I would like to have this done along with the user docs update I'm doing now.