- upgrade `webpack` and `webpack-cli` to latest major v5
  - (`webpack-dev-server` does not have a v5, is already at latest major)
  - fix config errors and deprecation warnings:
    - `[hash]` -> `[contenthash]` (https://webpack.js.org/migrate/5/#clean-up-configuration)
      - `contenthash` is just a better hash, as it is calculated per entrypoint instead for the entire bundle
        - that being said, we only have one entrypoint, so not super relevant. but `hash` was also deprecated
      - also same as [Argo CD config](https://github.com/argoproj/argo-cd/blob/6ca2e90b5094eba3878746fee5f2c357bfbc6cb8/ui/src/app/webpack.config.js#L20)
    - `node.fs: "empty"` -> `resolve.fallback.fs: false` (https://webpack.js.org/migrate/5/#clean-up-configuration)
      - also same as [Argo CD config](https://github.com/argoproj/argo-cd/blob/6ca2e90b5094eba3878746fee5f2c357bfbc6cb8/ui/src/app/webpack.config.js#L28)
    - `loaders` -> `use` (https://webpack.js.org/migrate/5/#update-outdated-options)
      - `!` syntax for chaining loaders has been fully removed as well. replaced by using arrays

- upgrade `HtmlWebpackPlugin` and `CopyWebpackPlugin` to latest major:
  - `html-webpack-plugin` to v5's main [breaking changes](https://github.com/jantimon/html-webpack-plugin/blob/v5.5.3/CHANGELOG.md#500-2021-02-03) are to drop support for Webpack v4 and Node <= 10
  - `copy-webpack-plugin` to v11 has some options changes as well as Webpack and Node support drops:
    - [v6](https://github.com/webpack-contrib/copy-webpack-plugin/blob/v11.0.0/CHANGELOG.md#600-2020-05-15) changes to use `patterns: [...]`
      - same syntax as [Argo CD config](https://github.com/argoproj/argo-cd/blob/6ca2e90b5094eba3878746fee5f2c357bfbc6cb8/ui/src/app/webpack.config.js#L72)
    - [v7](https://github.com/webpack-contrib/copy-webpack-plugin/blob/v11.0.0/CHANGELOG.md#700-2020-12-10) drops support for Webpack v4
    - [v8](https://github.com/webpack-contrib/copy-webpack-plugin/blob/v11.0.0/CHANGELOG.md#800-2021-03-04) does not impact our usage
    - v9-[v11](https://github.com/webpack-contrib/copy-webpack-plugin/blob/v11.0.0/CHANGELOG.md#1100-2022-05-17) drop support for older Node, now requiring Node >= 14.15.0
- no changes needed to `DefinePlugin`
- `MonacoEditorWebpackPlugin` is being upgraded in a separate PR/commit

- upgrade `style-loader` and `sass-loader` to latest major:
  - `style-loader`'s main breaking changes are dropping support for Webpack v4 and old Node versions:
    - [v1](https://github.com/webpack-contrib/style-loader/blob/v3.3.3/CHANGELOG.md#100-2019-08-06) drops support for Webpack < v4, Node < 8.9.0, and otherwise does not impact our usage
    - [v2](https://github.com/webpack-contrib/style-loader/blob/v3.3.3/CHANGELOG.md#200-2020-10-09) drops support for Node < 10.13.0 and otherwise does not impact our usage
    - [v3](https://github.com/webpack-contrib/style-loader/blob/v3.3.3/CHANGELOG.md#300-2021-06-24) drops support for Webpack v4, Node < 12.13.0, and otherwise does not impact our usage
  - `sass-loader`'s main breaking changes are dropping support for Webpack v4 and old Node versions:
    - [v11](https://github.com/webpack-contrib/sass-loader/blob/v13.3.2/CHANGELOG.md#1100-2021-02-05) drops support for Webpack v4
    - v12-[v13](https://github.com/webpack-contrib/sass-loader/blob/v13.3.2/CHANGELOG.md#1300-2022-05-18) drop support for older Node, now requiring Node >= 14.15.0
- did not touch `raw-loader` or `file-loader` as both are [deprecated in Webpack v5](https://webpack.js.org/guides/asset-modules/)
  - can replace these with native alternatives in a future PR
  - no deprecation warnings from these right now
- did not touch `source-map-loader`, `react-hot-loader`, `babel-loader`, or `ts-loader` as I'd like to replace these with `esbuild-loader`
  - as it would be much faster, still serves our minimal config needs, and matches [Argo CD config](https://github.com/argoproj/argo-cd/blob/6ca2e90b5094eba3878746fee5f2c357bfbc6cb8/ui/src/app/webpack.config.js#L37)
  - `react-hot-loader` is also [deprecated](https://github.com/gaearon/react-hot-loader#moving-towards-next-step)
  - no deprecation warnings from these right now

- also change some single quotes to double quotes in the config for consistency (`'` -> `"`)

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>

- this is no longer necessary with Webpack v5

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>

- `raw-loader`'s main breaking changes are dropping support for Webpack <v4 and old Node versions:
  - [v1](https://github.com/webpack-contrib/raw-loader/blob/v4.0.2/CHANGELOG.md#100-2018-12-10) drops support for Webpack < v4 and Node < 6.9
  - [v2](https://github.com/webpack-contrib/raw-loader/blob/v4.0.2/CHANGELOG.md#200-2019-03-18) does not seem to impact our usage
  - [v3](https://github.com/webpack-contrib/raw-loader/blob/v4.0.2/CHANGELOG.md#300-2019-06-05) drops support for Node < 8.9.0
  - [v4](https://github.com/webpack-contrib/raw-loader/blob/v4.0.2/CHANGELOG.md#400-2019-11-25) drops support for Node < 10.13.0
- I was not able to swap `raw-loader` for built-in Webpack v5 asset loading as it is an in-between loader
  - it would have to be replaced by `css-loader`, effectively, but doing that causes Webpack to fail to find assets from `argo-ui` etc
    - using `resolve-url-loader` or other trial-and-error attempts did not fix that either; not really sure why it's failing
- swap `file-loader` for built-in Webpack v5 `asset/resouce` loading

- downgrade `style-loader` to v1
  - [v2](https://github.com/webpack-contrib/style-loader/blob/v3.3.3/CHANGELOG.md#200-2020-10-09)'s breaking change in webpack-contrib/style-loader@7a0ce4c appears to break our usage
    - I believe this is because the chained `raw-loader` returns a String and not an Array. Updating `raw-loader` did not fix this (and its latest version is older than `style-loader` v2 as well)
    - this didn't cause a build error, but it caused styles to fail to load on render instead

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>