Support for HTML header comments in subgallery's readme.md

[AntoineD]

Fixes #85

[smarie]

Thanks @AntoineD . Can you please add a changelog.md entry for your PR ?

### 0.7.11 - (in progress)

 - (here)

(please look at the previous changelog entries as examples)

[AntoineD]

Thanks @AntoineD . Can you please add a changelog.md entry for your PR ?

### 0.7.11 - (in progress)

 - (here)

(please look at the previous changelog entries as examples)

Done.

[smarie]

I am not able to see this change @AntoineD , did you push the commit ?

[AntoineD]

I am not able to see this change @AntoineD , did you push the commit ?

My bad, sorry about that, that should be OK now.

[smarie]

Thanks @AntoineD !