feat: test linting of qmd

Author: jcken95

tests/testthat/in/lintr-fail.qmd

@@ -0,0 +1,8 @@
+---
+title: "Test doc: fail lintr"
+format: html
+---
+
+```{r}
+sum(1,2)
+```

tests/testthat/in/lintr-success.qmd

@@ -0,0 +1,8 @@
+---
+title: "Test doc: success lintr"
+format: html
+---
+
+```{r}
+sum(1, 2)
+```