Add mergify config for release 2021.03

[codecov[bot]]

Codecov Report

Merging #2285 (1ae159f) into master (1e7ca02) will decrease coverage by 0.04%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2285      +/-   ##
==========================================
- Coverage   91.31%   91.26%   -0.05%     
==========================================
  Files         199      199              
  Lines       11761    10966     -795     
  Branches     1583     1387     -196     
==========================================
- Hits        10739    10008     -731     
+ Misses        755      696      -59     
+ Partials      267      262       -5     

Impacted Files	Coverage Δ
src/garage/torch/optimizers/optimizer_wrapper.py	93.75% <0.00%> (-6.25%)	:arrow_down:
src/garage/sampler/env_update.py	82.92% <0.00%> (-3.62%)	:arrow_down:
src/garage/torch/optimizers/differentiable_sgd.py	86.66% <0.00%> (-3.34%)	:arrow_down:
src/garage/torch/policies/stochastic_policy.py	88.63% <0.00%> (-3.17%)	:arrow_down:
src/garage/torch/algos/trpo.py	91.66% <0.00%> (-3.08%)	:arrow_down:
src/garage/torch/algos/dqn.py	93.07% <0.00%> (-2.09%)	:arrow_down:
src/garage/torch/_functions.py	92.42% <0.00%> (-1.92%)	:arrow_down:
...rage/tf/optimizers/conjugate_gradient_optimizer.py	81.90% <0.00%> (-1.81%)	:arrow_down:
src/garage/np/_functions.py	77.39% <0.00%> (-1.74%)	:arrow_down:
src/garage/torch/algos/sac.py	97.14% <0.00%> (-1.66%)	:arrow_down:
... and 9 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 1e7ca02...1ae159f. Read the comment docs.