add: create new vignettes for introduction, study context, and sensitivity studies

refs #11

vignettes/V01-Introduction.Rmd

+---
+title: "V01 - Introduction"
+output: 
+  rmarkdown::html_vignette:
+    css: style.css
+vignette: >
+  %\VignetteIndexEntry{V01 - Introduction}
+  %\VignetteEngine{knitr::rmarkdown}
+  %\VignetteEncoding{UTF-8}
+---
+
+```{r setup, include = FALSE, file = 'setup.R'}
+rm(list = ls())
+gc()
+```

vignettes/V02-Study_context_and_data.Rmd

+---
+title: "V02 - Study context and data"
+output: 
+  rmarkdown::html_vignette:
+    css: style.css
+vignette: >
+  %\VignetteIndexEntry{V02 - Study context and data}
+  %\VignetteEngine{knitr::rmarkdown}
+  %\VignetteEncoding{UTF-8}
+---
+
+```{r setup, include = FALSE, file = 'setup.R'}
+rm(list = ls())
+gc()
+```

vignettes/V03-Sensitivity_studies_of_the_parameters_involved_in_the_LAI_simulation.Rmd

+---
+title: "V03 - Sensitivity studies of the parameters involved in the LAI simulation"
+output: 
+  rmarkdown::html_vignette:
+    css: style.css
+vignette: >
+  %\VignetteIndexEntry{V03 - Sensitivity studies of the parameters involved in the LAI simulation}
+  %\VignetteEngine{knitr::rmarkdown}
+  %\VignetteEncoding{UTF-8}
+---
+
+```{r setup, include = FALSE, file = 'setup.R'}
+rm(list = ls())
+gc()
+```