Theia: [dependency][core] Drop Node.js 10.x support

[kittaakos]

We will drop Node.js 10.x support in one of the next releases. This task should contain info about what should be done:

• [x] Notify the community (https://community.theia-ide.org/t/announcement-drop-support-for-node-10/900)
• [ ] Drop Node.js 10.x from the CI,
• [ ] Update the documentation (https://github.com/eclipse-theia/theia/issues/8184#issuecomment-659400743)
• [x] Potentially update theia-apps
• [ ] _(Add your item)_

Feature Description:

[mikael-desharnais]

Updating the documentation could be a good idea too :

• [x] [composing applications](https://theia-ide.org/docs/composing_applications/): https://github.com/theia-ide/theia-website/pull/124
• [ ] https://github.com/eclipse-theia/theia/blob/master/doc/Developing.md#prerequisites
• [ ] https://github.com/eclipse-theia/theia/blob/master/doc/Developing.md#building-on-windows

[akosyakov]

@marcdumais-work @vince-fugnitto Would you be able to take care of it? Some VS Code extension starts using Node.j12 APIs already: https://github.com/eclipse-theia/theia/issues/7608#issuecomment-663812240 We should get rid of Node.js 10 completely.

[vince-fugnitto]

@marcdumais-work @vince-fugnitto Would you be able to take care of it? Some VS Code extension starts using Node.j12 APIs already: #7608 (comment) We should get rid of Node.js 10 completely.

I'll pick it up for after this Thursday's release 👍

[vince-fugnitto]

I've added a theia-apps entry as I believe we will need to make some modifications as well.

[vince-fugnitto]

The theia-apps changes to drop Node 10: https://github.com/theia-ide/theia-apps/pull/391