Add support for FHIR validator's new watch mode

[vadi2]

See hapifhir/org.hl7.fhir.core#1311 - this (should) reduce validation time because the validator won't need to load all of the necessary packages at startup every single time you need to validate, and instead just once at the start of the bindary.

Relevant thread to read up on: https://chat.fhir.org/#narrow/stream/179239-tooling/topic/Validator.20CLI.20watch.20mode

[SvenSommer]

Hey @vadi2,
taking into consideration the details from the forum post, the new watch mode for the FHIR validator does indeed present an intriguing feature to integrate into the extension. It looks like it could significantly optimize the validation process by reducing the need to repeatedly load necessary packages.

The practical tips on using the -watch-mode are greatly appreciated. Given the details provided, it is clear that careful handling and timing are needed to prevent any issues such as race conditions or inconsistencies when files are updated.

Given this, I will begin planning the integration of the FHIR validator's "watch mode" into our extension. This task may require substantial work including adjusting the current implementation and extensive testing to ensure its reliable operation.

Again, thank you for bringing this new feature to my attention. I'll do my best to update the extension and I'll keep you posted on the progress.