Support aggregations and fix some bugs.

• README.md
• Update README.md
• Update README.md
• Refactor aggregations (#55)
• Support metric aggregation (#54)
• Support date range aggregation (#52)
• Support range aggregation (#51)
• Update proto file (#47)
• Support terms aggregation (#46)
• Allow the default analyzer to be set to index metadata (#45)
• Support sorting by field value (#44)
• Fix .env (#42)
• Add integration tests (#41)
• Remove options
• Change entrypoint
• Update integration tests
• Add port
• Update periodic_integrations.yml
• Downgrade etcd to 3.5.0
• Add options
• Rename test workflows
• Add periodic_integration.yml (#40)
• Add integration tests (#39)
• Fix bugs in tests caused by file path (#38)
• Skip the integration tests on windows platform (#37)
• Fixed a bug caused by file paths (#36)
• Update periodic tests (#35)
• Add periodic tests (#34)