Display online english guide

[ngocnhan-tran1996]

As report in

#3186

AFAIK, a newest maven version cause blank site.

Markdown conflict with Velocity on ## syntax:
Since ## denotes a single line comment in Velocity, Markdown headers using this syntax are suppressed from generated content.
You can use unparsed content syntax #[[##]]# or escape tool like ${esc.h}${esc.h}.

More detail maven-site-plugin

But I found the another way.
If markdown file does not contains # Title, only add tag h1

[coveralls]

coverage: 87.175%. remained the same
when pulling 2757fff on ngocnhan-tran1996:issues-3186
into 2e62ab5 on mybatis:master.

[hazendaz]

Thanks @ngocnhan-tran1996. I did not confirm but see no issue with the add. I'll check later as it seems we have some other issue with site not releasing when gh-pages is updated. I'll try to check this weekend.

[awxiaoxian2020]

I think this PR need to apply to all mybatis projects...