To html encoding add
- [x ] closes https://github.com/pandas-dev/pandas/issues/28663
- [x ] tests added / passed
- [x ] passes `black pandas`
- [x ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x ] whatsnew entry

added encoding argument to DataFrame.to_html()

hi @josibake , I found two checks failed but I just got `[error]Bash exited with code '1'` in azure log, could you give me some tips to fix this? hey @ailurus1991 , if you look further up in the logs, it says that running `black` changed two files.

try running `black pandas/core` commit those changes. @WillAyd if `encoding` is specified and not applicable we should presumably raise? Although I don't think it should be part of this PR. Something to think about so we're consistent across the IO methods. > @WillAyd if `encoding` is specified and not applicable we should presumably raise? Although I don't think it should be part of this PR. Something to think about so we're consistent across the IO methods.

https://github.com/pandas-dev/pandas/issues/28766#issuecomment-538413490  "We should raise when encoding is specified and it's buf isn't a string path." > Although I don't think it should be part of this PR.

maybe it should. Since this is effectively an enhancement then it may be worth getting it right off the bat. @ailurus1991 looks ok, can you add a whtasnew note in other enhancements section > @ailurus1991 looks ok, can you add a whtasnew note in other enhancements section

@jreback Hi Jeff, I added a simple whatsnew in doc, could you review it? thx thanks