SpanFinder into spaCy from experimental

[kadarakos]

Integrating the span_finder from spacy-experimental into spaCy.

Description

The SpanFinder is a component that suggest spans with a very simple tokenwise classifier: it decides for each token if it could be a start and/or end of a span. The code is largely just copied from spacy-experimental with the minimum amount of changes required to run the tests.

I added a couple of comments with the XXX annotation to ask a couple of initial questions about the parts I would consider changing after reading the code.

Types of change

Moving spacy-experimental component into spaCy.

Checklist

• I confirm that I have the right to submit this contribution under the project's MIT license.
• I ran the tests, and all new and existing tests passed.
• My changes don't require a change to the documentation, or if they do, I've added all required information.

[kadarakos]

Not sure why the project clone test fails in the Test Python39Linux?

[svlandeg]

Looks good to me! I only had a few minor comments.

[adrianeboyd]

I'll go ahead and merge this so we can include it in a dev release. I'll be testing it a lot with several demo projects, so if anything crops up we can fix it before the v3.6.0 release.

[svlandeg]

Thanks @kadarakos and @adrianeboyd for pushing this one over the line! 🙏