create ResponseUrlProvider

[BurnzZ]

Partially resolves #83.

The only thing missing here is ensuring that the providers are powerful enough such that having a dependency of HttpResponse and BrowserHtml would not trigger downloading the page twice (using the ResponseUrl from the BrowserHtml is preferred if available). However, web-poet needs to be updated to add a url component to BrowserHtml.

Checklist:

• Basic implementation
• Changelog

[codecov]

Codecov Report

Merging #87 (4055381) into master (7ac5fbe) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #87      +/-   ##
==========================================
+ Coverage   97.86%   97.88%   +0.02%     
==========================================
  Files          12       12              
  Lines         468      473       +5     
==========================================
+ Hits          458      463       +5     
  Misses         10       10              

Impacted Files	Coverage Δ
scrapy_poet/downloadermiddlewares.py	100.00% <ø> (ø)
scrapy_poet/page_input_providers.py	95.65% <100.00%> (+0.33%)	⬆️

[kmike]

Thanks @BurnzZ!