Desktop: when importing MD files create resources for local linked files (#2262)

* md importer: first pass import attachment resources with markdown files

* md importer: import resources from md - no unneeded saves, check if files exist, regex name

* md importer: test import of local files as resources, separate method for importing linked files, comment regex matching md tags

* md importer: move stateful regex to method scope, remove spurius await

* md importer: lint

* md importer: respond to PR comments: remove test nesting, test sample, check if path is dir, use shim.fsDriver

* md importer: use file-path methods for getting attachment path

* md importer: use extractImageUrls helper, test for file with zero links

* md importer: try catch around importLocalImages, improve test

* md importer: importing attached images cover case where link also appears elsewhere in doc

* md importer: only create 1 resource if note contains duplicate links, test

* md importer: remove log

* md importer: remove use of lodash