chore: rename the docs directory

README.md

docs/README.md

docs/img/caution.png

docs/img/dex-backend-flow.png

docs/img/dex-flow.png

docs/logos/dex-glyph-bw.png

docs/logos/dex-glyph-bw.svg

docs/logos/dex-glyph-color.png

docs/logos/dex-glyph-color.svg

docs/logos/dex-glyph-white.png

docs/logos/dex-glyph-white.svg

docs/logos/dex-horizontal-color.png

docs/logos/dex-horizontal-color.svg

docs/logos/dex-horizontal-white.png

docs/logos/dex-horizontal-white.svg

examples/config-dev.yaml

examples/grpc-client/README.md