Fix static files not found error in 0.8.4

[Korusuke]

Description

After #839, in release 0.8.4 swagger static files are returning 404 since they are not included in pypi dist

Motivation and Context

Issue reported by Bo Han on slack

How Has This Been Tested?

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature and improvements (non-breaking change which adds/improves functionality)
• Bug fix (non-breaking change which fixes an issue)
• Code Refactoring (internal change which is not user facing)
• Documentation
• Test, CI, or build

Component(s) if applicable

• BentoService (service definition, dependency management, API input/output adapters)
• Model Artifact (model serialization, multi-framework support)
• Model Server (mico-batching, dockerisation, logging, OpenAPI, instruments)
• YataiService gRPC server (model registry, cloud deployment automation)
• YataiService web server (nodejs HTTP server and web UI)
• Internal (BentoML's own configuration, logging, utility, exception handling)
• BentoML CLI

Checklist:

• My code follows the bentoml code style, both ./dev/format.sh and
  ./dev/lint.sh script have passed
  (instructions).
• My change reduces project test coverage and requires unit tests to be added
• I have added unit tests covering my code change
• My change requires a change to the documentation
• I have updated the documentation accordingly

[codecov]

Codecov Report

Merging #975 into master will increase coverage by 0.00%.
The diff coverage is 98.36%.

@@           Coverage Diff           @@
##           master     #975   +/-   ##
=======================================
  Coverage   62.86%   62.87%           
=======================================
  Files         123      123           
  Lines        8112     8115    +3     
=======================================
+ Hits         5100     5102    +2     
- Misses       3012     3013    +1     

Impacted Files	Coverage Δ
bentoml/adapters/json_input.py	57.89% <ø> (ø)
bentoml/saved_bundle/pip_pkg.py	81.61% <88.88%> (-12.92%)	⬇️
bentoml/artifact/artifact.py	93.06% <100.00%> (-2.12%)	⬇️
bentoml/artifact/h2o_model_artifact.py	88.88% <100.00%> (+51.74%)	⬆️
bentoml/cli/bento_service.py	71.42% <100.00%> (+0.18%)	⬆️
bentoml/saved_bundle/bundler.py	88.50% <100.00%> (-0.14%)	⬇️
bentoml/saved_bundle/local_py_modules.py	84.70% <100.00%> (ø)
bentoml/service.py	88.75% <100.00%> (+0.45%)	⬆️
bentoml/utils/__init__.py	69.11% <0.00%> (-7.36%)	⬇️
... and 5 more

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