mermaidjs can't render htmlLabels

[kierandg]

• mermaid htmlLabels does not work correctly, the tag <br/> is rendered but <span> is not
• The font awesome does not render at the editing time (just rendered after export)

```mermaid

%%{init: { 
    "theme": "forest",
    "flowchart": { "htmlLabels": true, "curve": "basis" }},
    "securityLevel": "loose"
}%%

flowchart LR

A[Text 1<br/><span style="color: red">text 2</span>] --> B["fa:fa-comment-dots<br/>Comment"]

**Expected result:**
The html part <span> of the label is rendered correctly