chore: build: upgrade webpack from 4 to 5 (#770)

* app node_modules: upgrade webpack to 4->5

Signed-off-by: Dorian Johnson <2020@dorianj.net>

* package.json: install path-browserify

Needed by react-markdown as of 5.0.2

Signed-off-by: Dorian Johnson <2020@dorianj.net>

* webpack: use polyfill for path

Signed-off-by: Dorian Johnson <2020@dorianj.net>

* webpack: add hack to make old react-bootstrap work

Signed-off-by: Dorian Johnson <2020@dorianj.net>

* package.json: upgrade html-webpack-plugin 4 -> 4.5.0

Signed-off-by: Dorian Johnson <2020@dorianj.net>

* package.json: upgrade mini-css-extract-plugin 0.10 -> 0.12

Fixes many webpack deprecation warnings.

Signed-off-by: Dorian Johnson <2020@dorianj.net>

* webpack: fix deprecation warning in moduleIds optimization

Signed-off-by: Dorian Johnson <2020@dorianj.net>

* webpack: link hacky behavior to ticket

#818

Signed-off-by: Dorian Johnson <2020@dorianj.net>