feat: Add basic support for bindings/go using CGO

[jiaoew1991]

This demo attempts to provide Go bindings by CGO, referring to the writing style of https://github.com/confluentinc/confluent-kafka-go/blob/master/kafka/build_dynamic.go.

To run the test, follow these steps:

1. Write an opendal_c.pc file, for example:

libdir=/path/to/opendal/target/debug/
includedir=/path/to/opendal/bindings/c/include/

Name: opendal_c
Description: opendal c binding
Version:

Libs: -L${libdir} -lopendal_c
Cflags: -I${includedir}

2. Set the PKG_CONFIG_PATH environment variable to include the path of opendal_c.pc, for example:

export PKG_CONFIG_PATH="${PKG_CONFIG_PATH}:/path/to/opendal_c.pc/"

3. Run go test:

go test -tags dynamic .

[Xuanwo]

1. Write an opendal_c.pc file

Learnt a lot.

[Xuanwo]

Cool, let's do this.

[Xuanwo]

Thanks a lot, let's go!