Add dependabot configuration

[yeikel]

See https://github.blog/2020-06-01-keep-all-your-packages-up-to-date-with-dependabot/

[codecov-commenter]

Codecov Report

Base: 66.90% // Head: 66.85% // Decreases project coverage by -0.04% ⚠️

Coverage data is based on head (31bce8e) compared to base (11a4513).
Patch has no changes to coverable lines.

❗ Current head 31bce8e differs from pull request most recent head 8ebcdd5. Consider uploading reports for the commit 8ebcdd5 to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3162      +/-   ##
============================================
- Coverage     66.90%   66.85%   -0.05%     
+ Complexity     4546     4543       -3     
============================================
  Files           248      248              
  Lines         14738    14738              
  Branches        916      916              
============================================
- Hits           9860     9853       -7     
- Misses         4487     4492       +5     
- Partials        391      393       +2     

Impacted Files	Coverage Δ
...ava/redis/clients/jedis/JedisClusterInfoCache.java	72.50% <0.00%> (-3.13%)	⬇️
src/main/java/redis/clients/jedis/JedisPubSub.java	70.00% <0.00%> (-1.82%)	⬇️

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