Code blocks in requirements break parsing

[jakobbraun]

Adding a code block like:

```md
## Test

test 123
```

... to the requirements file breaks the parsing. OFT seems to detect it as a new requirement.

Expected Behaviour:

• OFT ignored the headline in the code block (important)
• OFT prints the contents of the code block formated as code in the HTML output (nice to have)

[redcatbear]

I think I can solve this by adding a new state in the markdown parser that ignores literal sections (starting and ending with tripple-backticks).