Support service worker in all environments (dev and sdk)

[MidhunSureshR]

For authenticated media, we need a service worker running in both dev and sdk builds.

Tasks

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1. sw.js in build should contain list of assets to cache but the list should be empty when building the sdk.
2. There should be no update dialog when code changes in development server or sdk build.
3. version returned by sw.js when used in sdk context should be correct (as per base-manifest.json)
4. sw.js is served during dev - done by custom rollup plugin
5. supply notification icon for sdk build we can skip this until we want to support notifications in sdk
6. Unify defines in config and document why there's two sources of truth
7. Package sw.js in sdk build - preferably using the same plugin?
8. Document how to use the sdk with sw.js
9. During dev, version should be develop and global hash should be latest git commit.

[MidhunSureshR]

Done in #1181, #1179, #1174