Merge pull request #12 from simonpenel/main

Update README.md

README.md

@@ -5,3 +5,22 @@
 [![CRAN Downloads](https://cranlogs.r-pkg.org/badges/seqinr)](https://cran.r-project.org/package=seqinr)
 [![R-CMD-check](https://github.com/lbbe-software/seqinr/workflows/R-CMD-check/badge.svg)](https://github.com/lbbe-software/seqinr/actions)
 
+
+* seqinr on CRAN https://cran.r-project.org/web/packages/seqinr/index.html
+
+install seqinr from CRAN:
+```
+>install.packages("seqinr")
+
+```
+
+* seqinr on R-forge: https://seqinr.r-forge.r-project.org/
+
+* seqinr on github https://github.com/lbbe-software/seqinr
+
+install seqinr from github:
+
+```
+>library(devtools)
+>install_github("lbbe-software/seqinr")
+```