Add list projects method for GHUser

[t0m4uk1991]

Description

As was mentioned in #924, there is no method in GHUser to retrieve user project boards.
In scope of this PR listProjects method was added in GHUser.

[codecov]

Codecov Report

Merging #1183 (7dbccd2) into main (fb69457) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##               main    #1183      +/-   ##
============================================
+ Coverage     73.52%   73.54%   +0.01%     
- Complexity     1844     1846       +2     
============================================
  Files           186      186              
  Lines          6154     6158       +4     
  Branches        367      367              
============================================
+ Hits           4525     4529       +4     
  Misses         1408     1408              
  Partials        221      221              

Impacted Files	Coverage Δ
src/main/java/org/kohsuke/github/GHUser.java	56.36% <100.00%> (+3.42%)	⬆️

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