[docs][Distributed lock] add example to client doc

[hhunter-ms]

Description

Update client doc with distributed lock sample

Issue reference

PR will close: dapr/docs#2770

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (6c5aa60) 76.19% compared to head (f569696) 76.19%.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #930   +/-   ##
=========================================
  Coverage     76.19%   76.19%           
  Complexity     1433     1433           
=========================================
  Files           135      135           
  Lines          4399     4399           
  Branches        518      518           
=========================================
  Hits           3352     3352           
  Misses          766      766           
  Partials        281      281           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.