Task 8 - Fix: Annotate fun calls in RMarkdown

[jcrodriguez1989]

Fixes https://github.com/luisDVA/annotater/issues/8 I tested it with this code and seems to work, let me know if it works on your examples.

---
title: "Basic Rmarkdown Example"
author: "Your Name"
date: "`r Sys.Date()`"
output: html_document
---

# Introduction

This is an example of a simple Rmarkdown document.

\```{r}
library(annotater)
test_string <-c("library(boot)\nrequire(Matrix)")
writeLines(annotate_pkg_calls(test_string))
writeLines(annotate_repo_source(test_string))
writeLines(annotate_repo_source(test_string))
\```

\```{r}
library(annotater)
library("dplyr")
test_string <-c("library(boot)\nrequire(Matrix)")
writeLines(annotate_pkg_calls(test_string))
writeLines(annotate_repo_source(test_string))
writeLines(annotate_repo_source(test_string))
select(mtcars, mpg)
\```

[luisDVA]

Thanks! Functions now work smoothly with Rmd and Qmd files. I wasn't aware of knitr::purl, such a nice solution.

gracias Juan y aguante Córdoba