Enhance Dockerfile & Add Alpine image

[saiwas]

Relate to https://github.com/wangrongding/wechat-bot/issues/94

This PR has below changes:

• Refactor Dockerfile
• Optimizes the size of the Docker image
• Optimizes image build time
• Supporting switch to ALIYUN sources
• Support node alpine image

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Image Size:

REPOSITORY   TAG              IMAGE ID       CREATED        SIZE
wechat-bot   node-19-alpine   2b1c50d9a116   3 hours ago    844MB
wechat-bot   node-19          c46390dfe3d8   5 hours ago    1.95GB

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Usage:

# APT_SOURCE supports `default` and `aliyun`
docker build -t wechat-bot:node-19 --build-arg APT_SOURCE="aliyun" .
docker build -t wechat-bot:node-19-alpine -f Dockerfile.alpine --build-arg APT_SOURCE="aliyun" .