* Fix handling of empty `dependencies` section.
In Flipper, https://github.com/facebook/flipper/blob/master/website/package.json, all our dependencies live in `devDependecies` of our `package.json`. As a result `dependencies` is not set, causing a crash when running `yarn start`:
```
/Users/mweststrate/fbsource/xplat/sonar/website/node_modules/@docusaurus/core/bin/docusaurus.js:50
const siteDocusaurusPackagesForUpdate = Object.keys(sitePkg.dependencies)
^
TypeError: Cannot convert undefined or null to object
at Function.keys (<anonymous>)
at Object.<anonymous> (/Users/mweststrate/fbsource/xplat/sonar/website/node_modules/@docusaurus/core/bin/docusaurus.js:50:50)
at Module._compile (internal/modules/cjs/loader.js:955:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:991:10)
at Module.load (internal/modules/cjs/loader.js:811:32)
at Function.Module._load (internal/modules/cjs/loader.js:723:14)
at Function.Module.runMain (internal/modules/cjs/loader.js:1043:10)
at internal/main/run_main_module.js:17:11
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
```
Setting `"dependencies": {}`, works as work around, but this patch fixes the crash, and makes sure the deps are upgraded as well if they live in `devDependencies` instead of `dependencies`.
* formatting fix
ddc0f46b73