Update LoopBack 3 status to end-of-life (EOL)

This issue is to keep a consolidated list of pull requests to update the LoopBack 3 status from Maintenance LTS to End-of-Life (EOL).

- [ ] [eslint-config-loopback](https://github.com/strongloop/eslint-config-loopback)
- [x] [generator-loopback](https://github.com/strongloop/generator-loopback) (https://github.com/strongloop/generator-loopback/pull/420)
- [x] [gulp-loopback-sdk-angular](https://github.com/strongloop/gulp-loopback-sdk-angular) (https://github.com/strongloop/gulp-loopback-sdk-angular/pull/24)
- [x] [grunt-loopback-sdk-angular](https://github.com/strongloop/grunt-loopback-sdk-angular) (https://github.com/strongloop/grunt-loopback-sdk-angular/pull/40)
- [ ] [icars-server](https://github.com/strongloop/icars-server)
- [x] [loopback-next](https://github.com/strongloop/loopback-next) (https://github.com/strongloop/loopback-next/pull/6908) (TODO: #6969)
- [x] [loopback](https://github.com/strongloop/loopback) (https://github.com/strongloop/loopback/pull/4343)
- [ ] [loopback-api-definition](https://github.com/strongloop/loopback-api-definition)
- [x] [loopback-boot](https://github.com/strongloop/loopback-boot) (https://github.com/strongloop/loopback-boot/pull/308)
- [x] [loopback-cli](https://github.com/strongloop/loopback-cli) (https://github.com/strongloop/loopback-cli/pull/102)
- [ ] [loopback-component-oauth2](https://github.com/strongloop/loopback-component-oauth2)
- [ ] [loopback-component-explorer](https://github.com/strongloop/loopback-component-explorer)
- [ ] [loopback-component-passport](https://github.com/strongloop/loopback-component-passport)
- [ ] [loopback-component-push](https://github.com/strongloop/loopback-component-push)
- [x] [loopback-connector-remote](https://github.com/strongloop/loopback-connector-remote) (https://github.com/strongloop/loopback-connector-remote/pull/106)
- [x] [loopback-context](https://github.com/strongloop/loopback-context) (https://github.com/strongloop/loopback-context/pull/56)
- [x] [loopback-datasource-juggler](https://github.com/strongloop/loopback-datasource-juggler)(https://github.com/strongloop/loopback-datasource-juggler/pull/1888)
- [ ] [loopback-example-facade](https://github.com/strongloop/loopback-example-facade)
- [x] [loopback-filters](https://github.com/strongloop/loopback-filters) (https://github.com/strongloop/loopback-filters/pull/37)
- [ ] [loopback-getting-started](https://github.com/strongloop/loopback-getting-started)
- [ ] [loopback-getting-started-intermediate](https://github.com/strongloop/loopback-getting-started-intermediate)
- [ ] [loopback-multitenancy](https://github.com/strongloop/loopback-multitenancy)
- [ ] [loopback-multitenant-poc](https://github.com/strongloop/loopback-multitenant-poc)
- [ ] [loopback-phase](https://github.com/strongloop/loopback-phase)
- [ ] [loopback-sdk-angular-cli](https://github.com/strongloop/loopback-sdk-angular-cli)
- [ ] [loopback-soap](https://github.com/strongloop/loopback-soap)
- [ ] [loopback-swagger](https://github.com/strongloop/loopback-swagger)
- [ ] [loopback-utils](https://github.com/strongloop/loopback-utils)
- [ ] [loopback-workspace](https://github.com/strongloop/loopback-workspace)
- [x] [loopback.io](https://github.com/strongloop/loopback.io) (https://github.com/strongloop/loopback.io/pull/1125, https://github.com/strongloop/loopback.io/pull/1156)
- [ ] [poc-loopback-multitenancy](https://github.com/strongloop/poc-loopback-multitenancy)
- [ ] [strong-remoting](https://github.com/strongloop/strong-remoting)

Put a notice about LB3's EOL on the following pages.

- [ ] https://github.com/strongloop/loopback-next/tree/master/packages/booter-lb3app
- [ ] https://github.com/strongloop/loopback-next/tree/master/examples/lb3-application
- [ ] https://loopback.io/doc/en/lb4/migration-overview.html
- [ ] https://loopback.io/doc/en/lb4/migration-mounting-lb3app.html
- [x] https://loopback.io/doc/en/lb3/index.html