Update README.md

[cyriltovena]

Add oss-fuzz badge.

[kavirajk]

LGTM!

[codecov-io]

Codecov Report

Merging #3503 (5d4f92a) into master (e0f0ee0) will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3503      +/-   ##
==========================================
- Coverage   63.07%   63.03%   -0.05%     
==========================================
  Files         206      206              
  Lines       17701    17701              
==========================================
- Hits        11165    11157       -8     
- Misses       5535     5544       +9     
+ Partials     1001     1000       -1     

Impacted Files	Coverage Δ
pkg/promtail/targets/file/filetarget.go	64.13% <0.00%> (-2.76%)	⬇️
pkg/querier/queryrange/downstreamer.go	95.29% <0.00%> (-2.36%)	⬇️
pkg/querier/queryrange/limits.go	84.76% <0.00%> (-1.91%)	⬇️

[CLAassistant]

All committers have signed the CLA.

[stale]

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