Port the old Eclipse quickfixes to VS Code. See: https://github.com/theia-ide/yang-lsp/blob/master/yang-lsp/io.typefox.yang.ide/src/main/java/io/typefox/yang/ide/codeAction/CodeActionService.xtend * [Default implementation](https://github.com/eclipse/xtext-core/tree/master/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/codeActions) * [Example test](https://github.com/eclipse/xtext-core/blob/master/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/CodeActionTest.java) Add them to the `CodeActionProvider`.