add gitignore and vignette

.gitignore

-inst/doc
+#ignore gitignore !
+.gitignore
+
+# History files
+.Rhistory
+vignettes/.Rhistory
+
+# Example code in package build process
+*-Ex.R
+
+# R data files from past sessions
+.Rdata
+.RData
+..pdf
+..Rcheck
+
+# RStudio files
+.Rbuildignore
+.Rproj.user/
+fdf.Rproj
+
+# some generated files
+man/*.Rd
+# NAMESPACE

vignettes/start.Rmd

 ---
-title: "start"
+title: "Getting started"
 output: rmarkdown::html_vignette
 vignette: >
   %\VignetteIndexEntry{start}
@@ -17,7 +17,7 @@ knitr::opts_chunk$set(
 ```
 
 
-The package `fdf` allow to work with column-list. When for instance you have a list of time series that you want to include in a `data.frame`.
+The package `fdf` allows to work with column-list. When for instance you have a list of time series that you want to include in a `data.frame`.
 
 Since it works only with `data.frame` object, there is no new object, you can use very easily with any package like `dplyr` (and the tidyverse) and spatio-temporal object with package `sf` for instance.
 
@@ -25,28 +25,25 @@ Since it works only with `data.frame` object, there is no new object, you can us
 library(fdf)
 ```
 
-# Add a new column-list with `fd_add`
+### Add a new column-list with `fd_add`
 
 ```{r addData}
-DF = data.frame( A = 1:10)
+DF = data.frame( A = 1:5)
 
-DFD = fd_add(DF, "B", function(i) rnorm(runif(1, 4,20)))
+DFD = fd_add(DF, "B", function(i) round(rnorm(runif(1, 4,10))))
 DFD
 ```
 
-# Filter element in a column-list with `fd_filter`
+### Filter element in a column-list with `fd_filter`
 
 ```{r filter}
-fd_filter(DFD, "B", 1)
-
-fd_filter(DFD, "B", 2)
 
 fd_filter(DFD, "B", 3)
 ```
 
-# Find index of element in column-list matching with a key using `fd_match`
+### Find index of element in column-list matching with a key using `fd_match`
 
-```{r}
+```{r match}
 DFD = fd_add(DFD, "C", function(i) sample(1:5, 5))
 
 idMatch = fd_match(DFD, "C", 4)
@@ -56,22 +53,16 @@ idMatch
 fd_filter(DFD, "C", idMatch)
 ```
 
-# Melting column-list to a classical data.frame with `fd_melt`
+### Melting column-list to a classical data.frame with `fd_melt`
 
 ```{r meltSimple}
-fd_melt(DFD, "B")
-
-fd_melt(DFD, "B", keep = "A")
-
 fd_melt(DFD, "B", keep = list("A", "C"))
 ```
 
-when two column list have the same length for each elements, we can melt in the same time
+when two column-lists have the same length for each elements, we can melt in the same time
 
 ```{r meltDouble}
 DFD = fd_add(DFD, "B2", function(i) 1:length(DFD$B[[i]]))
 
-fd_melt(DFD, "B", "B2")
-
 fd_melt(DFD, "B", "B2", keep = list("A", "C"))
 ```