Add design for upload tgz file proposal

[knolleary]

This design adds the ability to upload a module's tgz file via the /nodes admin end point.

This will allow nodes to be installed that have been generated locally and not published to npm.

There will be some restrictions on where this can be used - for example, it will only be available with the built-in localfilesystem storage plugin.

The feature can be disabled via the editorTheme.palette.upload setting.

As this is the second design note related to node installation, this PR also reorganises the existing design note so we have a collection of designs on this topic.

For ease of review, here's a direct link to the upload-tgz design note: https://github.com/node-red/designs/blob/tgz-upload/designs/node-installation/upload-tgz.md

[hardillb]

Adding link to SO question about this sort of thing for reference https://stackoverflow.com/questions/63363349/is-there-a-way-to-install-a-nodered-node-in-a-remote-server/63365092

[LeiZhen-si]

I try upload module tgz file , but failure by lastest version. Error is
Error: Module not found
at checkModulePath (/usr/local/lib/node_modules/node-red/node_modules/@node-red/registry/lib/installer.js:88:15)
at Unpack.tar.x.on.on (/usr/local/lib/node_modules/node-red/node_modules/@node-red/registry/lib/installer.js:381:34)
at Unpack.emit (events.js:198:13)
at Unpack.[maybeClose] (/usr/local/lib/node_modules/node-red/node_modules/@node-red/registry/node_modules/tar/lib/unpack.js:195:12)
at Unpack.[unpend] (/usr/local/lib/node_modules/node-red/node_modules/@node-red/registry/node_modules/tar/lib/unpack.js:439:21)
at fs.close.er (/usr/local/lib/node_modules/node-red/node_modules/@node-red/registry/node_modules/tar/lib/unpack.js:346:55)
at /usr/local/lib/node_modules/node-red/node_modules/graceful-fs/graceful-fs.js:61:14
at FSReqWrap.args [as oncomplete] (fs.js:140:20)

[knolleary]

@gaoguijie please raise an issue on the main node-red repository: https://github.com/node-red/node-red