Start new unit tests, fix a hidden bug in watcher

.gitignore

.vscode/launch.json

package-lock.json

package.json

src/completion/completer/package.ts

src/core/file.ts

src/core/watcher.ts

src/lw.ts

test/fixtures/unittest/.vscode/settings.json

test/fixtures/unittest/01_core_file/01/another.bib

test/fixtures/unittest/01_core_file/01/auxfiles/another.fls

test/fixtures/unittest/01_core_file/01/main.bib

test/fixtures/unittest/01_core_file/01/main.fls

test/fixtures/unittest/01_core_file/01/main.tex

test/fixtures/unittest/01_core_file/01/output/main.fls

test/fixtures/unittest/01_core_file/01/subdir/sub.bib

test/runTest.ts

test/units/01_core_file.test.ts

test/units/02_core_watcher.test.ts

test/units/index.ts