Aside code cleanup

[ShayPunter]

Fixes GoogleChrome/webdev-infra#77

Changes proposed in this pull request:

• Migrates the aside component to webdev-infra
• A clean up of the now unused aside files in d.c.c.
• Updated handbook components documentation to include tip aside, objective aside & celebration aside

[google-cla]

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[chrome-devrel-infra]

❌ Failed to build (static) the site for commit c44392d. Building the site (npm run production) failed with the following error output:

[14:24:39] 'sass' errored after 422 ms
[14:24:39] Error: Can't find stylesheet to import.
   ╷
16 │ @import 'node_modules/webdev-infra/shortcodes/Aside/styles';
   │         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   ╵
  site/_scss/main.scss 16:9  root stylesheet
    at Object._newRenderError (/workspace/node_modules/sass/sass.dart.js:13478:19)
    at Object._wrapException (/workspace/node_modules/sass/sass.dart.js:13321:16)
    at StaticClosure._renderSync (/workspace/node_modules/sass/sass.dart.js:13296:18)
    at Object.Primitives_applyFunction (/workspace/node_modules/sass/sass.dart.js:1085:30)
    at Object.Function_apply (/workspace/node_modules/sass/sass.dart.js:6003:16)
    at _callDartFunctionFast (/workspace/node_modules/sass/sass.dart.js:7672:16)
    at Object.renderSync (/workspace/node_modules/sass/sass.dart.js:7650:18)
    at /workspace/gulp-tasks/sass.js:32:34
    at Array.forEach (<anonymous>)
    at sass (/workspace/gulp-tasks/sass.js:31:15)
[14:24:39] 'default' errored after 430 ms
ERROR: "gulp" exited with 1.

Check the Stage (dcc-staging) check status for more details.

[jimjiminyjimjim]

lgtm

[matthiasrohmer]

Won't fix, due to the pending move to the new CMS.