**Apache Airflow version**: 1.10.11

**Environment**: Python 3.7

- **Cloud provider or hardware configuration**:
- **OS** (e.g. from /etc/os-release): PRETTY_NAME="Debian GNU/Linux 10 (buster)"
 (from python3.7-slim-buster docker image)
- **Kernel** (e.g. `uname -a`): Linux 5.4.0-42-generic #46-Ubuntu SMP Fri Jul 10 00:24:02 UTC 2020 x86_64 GNU/Linux
- **Install tools**:
- **Others**:

**What happened**:

Using a markdown formatted table does not work.

**What you expected to happen**:

To be able to see a formated table within DAG view

**How to reproduce it**:

Add a tabular formatted code do dag.doc_md.

Example:

> mytable:
> 
> | a | b | c |
> | ------------- | ------------- | ------------- |
> | a | b | c |

[Table not formatted](https://i.imgur.com/l6JXuWe.png)

**Anything else we need to know**: N/A

airflow/www/utils.py
"""Gets 'state' & returns a formatted string with HTML for a given State"""
    state = attr.get('state')
    return state_token(state)
def nobr_f(attr_name):
    """Returns a formatted string with HTML with a Non-breaking Text element"""
    def nobr(attr):
        f = attr.get(attr_name)
        return Markup("<nobr>{}</nobr>").format(f)  
    return nobr
def datetime_f(attr_name):
    """Returns a formatted string with HTML for given DataTime"""
    def dt(attr):  
        f = attr.get(attr_name)
        as_iso = f.isoformat() if f else ''
        if not as_iso:
            return Markup('')
        f = as_iso
        if timezone.utcnow().isoformat()[:4] == f[:4]:
            f = f[5:]
        
        return Markup('<nobr><time title="" datetime="{}">{}</time></nobr>').format(as_iso, f)  
    return dt
def json_f(attr_name):
    """Returns a formatted string with HTML for given JSON serializable"""
    def json_(attr):
        f = attr.get(attr_name)
        serialized = json.dumps(f)
        return Markup('<nobr>{}</nobr>').format(serialized)  
    return json_
def dag_link(attr):