chore(renovate): set update schedule to monthly and group related updates together

[g-husam]

This should minimize noise and disruption by creating update PRs every month, instead of as and when new versions become available, and by grouping together related version bumps and all patch version bumps.

See https://docs.renovatebot.com/presets-config/#configbest-practices for more info.

NOTE: Security updates should still be created immediately, as that is the default and can be customized via vulnerabilityAlerts in the json config.

The packageRules take precedence over inherited configs, so all patch updates will be grouped together. Beyond that, anything matching a group config will be grouped together (such as well known monorepos and other curated lists of packages).

Also updating to json5 format to legally allow for comments.

Validated locally:

$ npx --yes --package renovate -- renovate-config-validator
 INFO: Validating .github/renovate.json5
 INFO: Config validated successfully against 1 file(s)

[aandreassa]

We will merge this next week after the break!