package: Fix npm watch* scripts
package: Fix npm watch* scripts

- elm sources are in gui/elm/, not src/elm/
- yarn gui:build:elm is now build:elm
- Ensure watch:js also lints gui/js/**
- yarn gui:lint was removed, run eslint on changed file instead

cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,nono/cozy-desktop,nono/cozy-desktop,cozy-labs/cozy-desktop,nono/cozy-desktop,nono/cozy-desktop