chore: Relates to #309. Update to Electron v4.0.1

In the Babel 7 migration guide these are the different plugings and
to add them:

See https://babeljs.io/blog/2018/07/27/removing-babels-stage-presets#migrating

```
// Stage 0
"@babel/plugin-proposal-function-bind",

// Stage 1
"@babel/plugin-proposal-export-default-from",
"@babel/plugin-proposal-logical-assignment-operators",
["@babel/plugin-proposal-optional-chaining", { "loose": false }],
["@babel/plugin-proposal-pipeline-operator", { "proposal": "minimal" }],
["@babel/plugin-proposal-nullish-coalescing-operator", { "loose": false }],
"@babel/plugin-proposal-do-expressions",

// Stage 2
["@babel/plugin-proposal-decorators", { "legacy": true }],
"@babel/plugin-proposal-function-sent",
"@babel/plugin-proposal-export-namespace-from",
"@babel/plugin-proposal-numeric-separator",
"@babel/plugin-proposal-throw-expressions",

// Stage 3
"@babel/plugin-syntax-dynamic-import",
"@babel/plugin-syntax-import-meta",
["@babel/plugin-proposal-class-properties", { "loose": false }],
"@babel/plugin-proposal-json-strings"
```

Fixes errors:

```
{ Error: Cannot find module '@babel/plugin-proposal-class-properties' from '/Users/scon/code/src/paritytech/fether/packages/fether-ui'
```

```
Failed to minify the bundle. Error: static/js/main.f19a0eac.chunk.js from Terser
TypeError: Cannot read property 'minify' of undefined
```

Fix sync rate not showing

fix: Fixes #383. Add an underlay to absorb a blur click away from the menu so nothing else in the UI clicked upon menu blur

fix: Fix txStatus race condition in sendStore

feat: Relates to #337. Part 1 of 2 - Account view - Change header account design

refactor: Rename handleMenuOpen to onOpen and same to close. Remove unnecesary isMenuOpen from child

for good measure

Might fix https://github.com/paritytech/fether/issues/379
Previously, we would resolve the promise and then set `this.txStatus`. However, resolving the promise actually redirects to `Sent` which expects `txStatus` to already be defined

fix: Relates to #324. Show link to Blockscout upon confirmed, not the first confirmation

feat: Relates to #264. SUI-based drop-down menu with Backup Account and Add Tokens

See https://github.com/sharegate/craco/issues/61.
Updating to craco 3.3.1 resolves error when trying to install dependencies and build:
```
Error: Cannot find module '~/code/src/paritytech/fether/node_modules/react-scripts/config/webpack.config.dev'
```

* Remove useless .header-container

* Add width to .account_information to fit full title width

* Use `flex-grow` instead of abbreviation `flex`

* Use justify-content: left to align account info and avatar to left and remove flex: 0 from .header-tokens