Apollo-android: Support JS target in multiplatform projects

[omainegra]

Is your feature request related to a problem? Please describe.

• Many projects include a JS target. Supporting JS targets will increase Apollo’s viability when being considered for multi-platform projects.
• It is not straightforward to use Apollo in projects that include a JS target. This is due to the apollo-runtme-kotlin artifact, which can’t be used in commonMain. One workaround is to include apollo-runtime-kotlin-jvm in androidMain and apollo-runtime-kotlin-ios-x64 in iosMain, then write dozen of expect/actual to fill the gap in jsMain

Describe the solution you'd like

• Add js target in the build definition.
• Provide actual implementations for the required classes (i.e ApolloHttpNetworkTransport).
• Probably many more things.

[martinbonnin]

Linking the work in progress:

• https://github.com/apollographql/apollo-android/pull/2467
• https://github.com/apollographql/apollo-android/pull/2482

[martinbonnin]

apollo-api will be able to target JS with 2.2.4 (see #2467). Updated todo list:

• [x] add a JS target to apollo-api
• [ ] implement ApolloHttpNetworkTransport for JS
• [ ] implement WebSocketFactory for JS