upgrade @babel/core to at least 7.9 to fix bug preventing installation

[xloem]

This partial upgrade fixes this installation error on yarn install with new versions of node, described at nodejs/node#32852 :

Error: Cannot find module 'node_modules/@babel/preset-env/node_modules/@babel/compat-data/data/corejs3-shipped-proposals'
    at createEsmNotFoundErr (internal/modules/cjs/loader.js:842:15)
    at finalizeEsmResolution (internal/modules/cjs/loader.js:835:15)
    at resolveExports (internal/modules/cjs/loader.js:424:14)
    at Function.Module._findPath (internal/modules/cjs/loader.js:464:31)
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:802:27)
    at Function.Module._load (internal/modules/cjs/loader.js:667:27)
    at Module.require (internal/modules/cjs/loader.js:887:19)
    at require (internal/modules/cjs/helpers.js:74:18)
    at Object.<anonymous> (/home/karl/git/test/2-install/dweb-archive/node_modules/@babel/preset-env/lib/polyfills/corejs3/usage-plugin.js:10:55)
    at Module._compile (internal/modules/cjs/loader.js:999:30) {
  code: 'MODULE_NOT_FOUND',
  path: 'node_modules/@babel/preset-env/node_modules/@babel/compat-data/package.json'
}
error Command failed.
Exit code: 1
Command: pika-web

Note: a quick way to bring dependencies fully up to date is yarn upgrade --latest.

[mitra42]

Thanks

[xloem]

note 2: sorry, this apparently needs a yarn.lock update too, to actually fix the issue for a new checkout. i'm going to try to add ci scripts locally before making more changes, to get my changes in better shape before sharing them.

[mitra42]

This was merged, so I think any such change will eed to be in a new PR (but I think you did a yarn.lock update in another PR so I'm presuming its OK ?

[xloem]

yeah, #200 is the followup to my error in this PR that I was referring to