UI investigation / demo for 3839 (do not merge).

[johnPhillips]

Summary

Addresses issue #3839

Relevant technical choices

I brute-forced a very basic implementation of the Menu component from Material UI to demo some of the ideas discussed here: #3920

Note that this was quickly knocked together just to visualise what these ideas might look like; I've disabled functionality of the buttons etc.

Checklist

• My code is tested and passes existing unit tests.
• My code has an appropriate set of unit tests which all pass.
• My code is backward-compatible with WordPress 4.7 and PHP 5.6.
• My code follows the WordPress coding standards.
• My code has proper inline documentation.
• I have added a QA Brief on the issue linked above.
• I have signed the Contributor License Agreement (see https://cla.developers.google.com/).

[github-actions]

Size Change: +10.2 kB (+1%)

Total Size: 1.13 MB

Filename	Size	Change
./dist/assets/css/admin.css	38.6 kB	+13 B (0%)
./dist/assets/js/googlesitekit-activation.********************.js	38 kB	-75 B (0%)
./dist/assets/js/googlesitekit-adminbar.********************.js	30.8 kB	-33 B (0%)
./dist/assets/js/googlesitekit-api.********************.js	9.15 kB	+4 B (0%)
./dist/assets/js/googlesitekit-dashboard-details.********************.js	43.9 kB	-36 B (0%)
./dist/assets/js/googlesitekit-dashboard-splash.********************.js	52.1 kB	+44 B (0%)
./dist/assets/js/googlesitekit-dashboard.********************.js	44.2 kB	-40 B (0%)
./dist/assets/js/googlesitekit-datastore-forms.********************.js	8.87 kB	+10 B (0%)
./dist/assets/js/googlesitekit-datastore-location.********************.js	2.02 kB	-8 B (0%)
./dist/assets/js/googlesitekit-datastore-ui.********************.js	8.82 kB	-6 B (0%)
./dist/assets/js/googlesitekit-datastore-user.********************.js	20.8 kB	-199 B (-1%)
./dist/assets/js/googlesitekit-idea-hub-post-list.********************.js	23.9 kB	-70 B (0%)
./dist/assets/js/googlesitekit-module.********************.js	44 kB	-78 B (0%)
./dist/assets/js/googlesitekit-modules-adsense.********************.js	44.6 kB	-54 B (0%)
./dist/assets/js/googlesitekit-modules-analytics-4.********************.js	19 kB	-5 B (0%)
./dist/assets/js/googlesitekit-modules-analytics.********************.js	65.6 kB	-9 B (0%)
./dist/assets/js/googlesitekit-modules-idea-hub.********************.js	22.7 kB	-553 B (-2%)
./dist/assets/js/googlesitekit-modules-optimize.********************.js	18.4 kB	+27 B (0%)
./dist/assets/js/googlesitekit-modules-pagespeed-insights.********************.js	16.5 kB	+71 B (0%)
./dist/assets/js/googlesitekit-modules-search-console.********************.js	28.4 kB	-159 B (-1%)
./dist/assets/js/googlesitekit-modules-tagmanager.********************.js	30 kB	-18 B (0%)
./dist/assets/js/googlesitekit-modules.********************.js	16.6 kB	+12 B (0%)
./dist/assets/js/googlesitekit-settings.********************.js	48.3 kB	-61 B (0%)
./dist/assets/js/googlesitekit-user-input.********************.js	45.1 kB	-72 B (0%)
./dist/assets/js/googlesitekit-vendor.********************.js	324 kB	+11.6 kB (+4%)
./dist/assets/js/googlesitekit-widgets.********************.js	11.5 kB	+5 B (0%)
./dist/assets/js/googlesitekit-wp-dashboard.********************.js	32.7 kB	-119 B (0%)
./dist/assets/js/runtime.********************.js	1.19 kB	+2 B (0%)

ℹ️ View Unchanged

Filename	Size
./dist/assets/css/adminbar.css	8 kB
./dist/assets/css/wpdashboard.css	4.58 kB
./dist/assets/js/32.********************.js	3.12 kB
./dist/assets/js/analytics-advanced-tracking.js	769 B
./dist/assets/js/googlesitekit-base.********************.js	1.59 kB
./dist/assets/js/googlesitekit-data.********************.js	1.65 kB
./dist/assets/js/googlesitekit-datastore-site.********************.js	13.3 kB
./dist/assets/js/googlesitekit-i18n.js	3.92 kB
./dist/assets/js/googlesitekit-idea-hub-notice.********************.js	2.4 kB
./dist/assets/js/googlesitekit-polyfills.********************.js	378 B

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