continue on error (#65)

Add an option to continue on error (most likely: R CMD CHECK error) from
[default
false](https://yihui.org/knitr/options/#:~:text=Note%20that%20R%20Markdown%20has%20changed%20this%20default%20value%20to%20FALSE.)
into true. This allows process to finish so that repo maintainers will
see what's wrong in case of errors. For now, it's only this:

```
  |..........................................                            |  60%
label: r_cmd_check (with options) 
List of 2
 $ echo: logi FALSE
 $ eval: logi TRUE

Quitting from lines 160-172 (template.Rmd) 
```

There are multiple reports that this message is not really helpful.

This has a significant side effect that fail of R CMD CHECK will not
fail the workflow anymore and the whole workflow will almost always
succeed. My assumption is that CHECK is usually executed in a separate,
obligatory workflow and validation is an optional artefact that would
have to be investigated. Please share your thoughts if you strongly
disagree with that.

Workflow fail is definitely implementable but this would require changes
in both validator and validator action. Validator would have to finish
the process and _return_ the information about the failure to the action
to pick up and fail (if needed).
Also: we would have to move upload report step from parent action into
here as fail needs to happen only after upload.

Signed-off-by: Pawel Rucki <[email protected]>

Author: pawelru

template.Rmd

@@ -35,6 +35,7 @@ library(magrittr)
 library(knitr)
 library(kableExtra)
 knitr::opts_chunk$set(
+  error = TRUE,
   width = 80L,
   comment = ""
 )