More ammonia builder options

[gsmedley]

There are some ammonia builder options it would be really nice to have:

• add_tag (Add additonal whitelisted tags without overwriting old ones.)
• filter_style_properties (Only allows the specified properties in style attributes.)

[zerolab]

First off, thank you for this most useful library!

I agree with @gsmedley that some of the new ammonia options would come in quite handy, especially filter_style_properties (rust-ammonia/ammonia#208)

[messense]

The current API does not scale well with more ammonia options, we should refactor it first.

[xmo-odoo]

Do you already have a vision for a new API?

[messense]

we could have a Builder that builds a Cleaner, something like:

cleaner = Builder()
    .tags({"a", "div"})
    .url_schemes({"http://", "https://"})
    .build()
cleaner.clean(html)

[xmo-odoo]

Ah so more something closer to upstream ammonia's behaviour?