(developer docs): updated docs for cross-platforms sdks

[cnlangzi]

• gosdk(docs): updated README.md to add how to expose gosdk methods in mobile sdk
• gosdk(docs): updated README.md to add how to expose gosdk methods in wasm sdk
• gosdk(docs): updated README.md to add how to expose gosdk methods in windows sdk

[boddumanohar]

docs from gobind https://pkg.go.dev/golang.org/x/mobile/cmd/gobind#hdr-Type_restrictions

Type_restrictions
All exported symbols in the package must have types that are supported. Supported types include:

- Signed integer and floating point types.

- String and boolean types.

- Byte slice types. Note that byte slices are passed by reference, and support mutation.

- Any function type all of whose parameters and results have supported types. Functions must return either no results, one result, or two results where the type of the second is the built-in 'error' type.

- Any interface type, all of whose exported methods have supported function types.

- Any struct type, all of whose exported methods have supported function types and all of whose exported fields have supported types.
-