add /build to .gitignore

.gitignore

...aAugment_library/autoaugment_learners/aa_learners.doctree

...rated/MetaAugment.autoaugment_learners.aa_learner.doctree

...ated/MetaAugment.autoaugment_learners.gru_learner.doctree

...Augment.autoaugment_learners.randomsearch_learner.doctree

docs/build/doctrees/environment.pickle

docs/build/doctrees/index.doctree

docs/build/doctrees/usage/autoaugment_helperclass.doctree

docs/build/doctrees/usage/tutorial_for_team.doctree

docs/build/html/.buildinfo

...MetaAugment_library/autoaugment_learners/aa_learners.html

...enerated/MetaAugment.autoaugment_learners.aa_learner.html

...nerated/MetaAugment.autoaugment_learners.gru_learner.html

...etaAugment.autoaugment_learners.randomsearch_learner.html

..._modules/MetaAugment/autoaugment_learners/aa_learner.html

...modules/MetaAugment/autoaugment_learners/gru_learner.html

...etaAugment/autoaugment_learners/randomsearch_learner.html

docs/build/html/_modules/index.html

...aAugment_library/autoaugment_learners/aa_learners.rst.txt

...rated/MetaAugment.autoaugment_learners.aa_learner.rst.txt