gha-merge-up - Merge-up javascript

[emteknetnz]

Follow up issue from https://github.com/silverstripeltd/product-issues/issues/753

gha-merge-up currently does not support js files, instead it will fail any build that includes client/ in the files diff

ACs

• Diffs that include client/ filter are allowed
• If changes in the client/ are detected, for non silverstripe/admin modules, silverstripe/admin is installed in a sibling directory and yarn install is run (see gha-update-js for how to do this)
• nvm use <correct_version> is run where correct_version is correct for the major version being merged-into
• yarn build is run in the module being merged-up
• The build fails if there is any issue with yarn build
• Any updated dist files are git added
• Initially, only asset-admin will use this functionality

Follow up issues created

• Use non-consts method of detecting installer version to use gha-generate-matrix#59

PRs

• ENH Rebuild client/dist on merge-up #6
• MNT Add merge-up workflow silverstripe-asset-admin#1375

[GuySartorelli]

PRs merged, all ACs met.