Update Header Logic Handling

[VarunS1997]

From Dirk:

Looks like there is a bug in your markdown export. In my text on TTM, I definitely have a space between the header markers (e.g., ###) and the header text, however, when it is exported, there is no more space between the markers and the text. So, for example, ### Header 3 is exported ###Header 3 and if forces to go through all my exports and correct them before I print to PDF.

[VarunS1997]

Likely related, the logic for headers is slightly unintuitive.

We shouldn't increase header levels if there's no level 1 already.

Intended Logic: if you have a page called "Fireball" and it contains:

# Header 1
Blah blah 1

## Header 2
Blah Blah 2

The exported markdown will be

# Fireball
## Header 1
Blah blah 1

### Header 2
Blah Blah 2

[VarunS1997]

and if you have:

## Header 1
Blah blah 1

## Header 2
Blah Blah 2

It will become

# Fireball
## Header 1
Blah blah 1

## Header 2
Blah Blah 2