Structure of headers in toc

[soonraah]

Thank you for a good theme. I love it 😄

I suggest to improve toc structures. When I write a Markdown of content like below,

+++
toc = true
+++

## Foo

### Foo 1

...

### Foo 2

...

## Bar

### Bar 1

...

(including words > 400)

its toc appears like below on my website.

Foo
Foo1
Foo2
Bar
Bar1

The structure of headers is not applied in toc. All headers look like in parallel. I think it's better to apply structures like below.

Foo
  Foo1
  Foo2
Bar
  Bar1

How do you think? (Of course, I know I can fix it by custom.css for me)

[soonraah]

In my case it works with #16.

[7hacker]

+1 would like this feature as well, the above PR works but I'm not clear what the app.css changes include and if they have any other effect? @soonraah

[7hacker]

Just found that app.css in the above PR only contains one additional style (below) so Im just going to adapt this for my usage of the toc, thanks @soonraah

.toc>nav li>ul{padding-left:1em}.cdata