Spike: Switch from lerna to pnpm workspaces

Nadie ha tomado este issue todavía.

Our current lerna-based setup is very inefficient. Most of the pull requests in this repository are created by RenovateBot to update package-lock files, our git history is full of RenovateBot commits that make it difficult to spot relevant changes.

Let's investigate how to switch from lerna to [pnpm](https://pnpm.js.org/) and use a single root package-lock file for the entire monorepo.

References:
- pnpm workspaces: https://pnpm.js.org/en/workspaces
- Travis CI setup: https://pnpm.js.org/en/continuous-integration#travis

Topics to investigate:
- How to release new versions using conventional release process? Can we perhaps use https://github.com/atlassian/changesets? Related: https://github.com/pnpm/pnpm/issues/2225
- Does RenovateBot support pnpm? If not, is there any other bot we could use instead? E.g. GitHub's [Dependabot](https://github.com/dependabot). Related: https://github.com/renovatebot/renovate/issues/2015

Comienza con las referencias a pnpm workspaces y Travis CI en el issue y, después, examina los workflows actuales de Lerna, package-lock, RenovateBot y releases. Se considerará terminado cuando se documente un plan de migración viable, incluido el manejo de releases y el soporte para actualizaciones de dependencias, en lugar de realizar un cambio de implementación.

Escrito por el modelo de indexación a partir del texto del issue.