Introduce dependabot config

[oliviertassinari]

Closes #1615
Closes #1612
Closes #1482
Closes #1598

Motivated by #1592 (comment)

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[codecov]

Codecov Report

Merging #1632 into next will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             next    #1632   +/-   ##
=======================================
  Coverage   89.76%   89.76%           
=======================================
  Files          73       73           
  Lines        2315     2315           
  Branches      420      420           
=======================================
  Hits         2078     2078           
  Misses        190      190           
  Partials       47       47           

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[dmtrKovalenko]

thanks!