allow to update query string using mod operator

[vanyakosmos]

What do these changes do?

update query string using mod operator

Are there changes in behavior for the user?

url = URL('https://example.com') % {'a': '1'}
assert str(url) == 'https://example.com?a=1'

Related issue number

close #434

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> (e.g. 588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the PR
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: Fix issue with non-ascii contents in doctest text files.

[codecov]

Codecov Report

Merging #435 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #435      +/-   ##
==========================================
+ Coverage   99.24%   99.25%   +0.01%     
==========================================
  Files           2        2              
  Lines         664      673       +9     
  Branches      152      154       +2     
==========================================
+ Hits          659      668       +9     
  Misses          5        5              

Impacted Files	Coverage Δ
yarl/__init__.py	99.01% <100.00%> (+0.01%)	⬆️

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[webknjaz]

close #434

that issue suggests // and you're using % here..

[webknjaz]

I think the UX research part is missing here: #434 (comment)

[asvetlov]

I like this PR and can buy it.

Please make the following before the merge:

1. Document % in docs/api.rst. docs/index.rst and README.rst should probably be updated as well to promote the new syntax instead of update_query() / with_query() calls.
2. Update __init__.pyi to reflect the new method.
3. Add CHANGES/435.feature file with a short one-line announcement for the feature.

[asvetlov]

The steps above are required to make the PR done.

[asvetlov]

Looks good, please apply my comments.