gnu: Add r-servr.

* gnu/packages/web.scm (r-servr): New variable.

gnu/packages/web.scm

@@ -2910,3 +2910,28 @@ (define-public r-jsonlite
 all edge cases are encoded and decoded consistently for use with dynamic data
 in systems and applications.")
     (license l:expat)))
+
+(define-public r-servr
+  (package
+    (name "r-servr")
+    (version "0.2")
+    (source (origin
+              (method url-fetch)
+              (uri (cran-uri "servr" version))
+              (sha256
+               (base32
+                "0gah99snaj8lk5zfzbxi3jwvpnlff9diz9gqv4qalfxpmb7fp6lc"))))
+    (build-system r-build-system)
+    (propagated-inputs
+     `(("r-httpuv" ,r-httpuv)
+       ("r-jsonlite" ,r-jsonlite)
+       ("r-mime" ,r-mime)))
+    (native-inputs
+     `(("r-rcpp" ,r-rcpp)))
+    (home-page "https://github.com/yihui/servr")
+    (synopsis "Simple HTTP server to serve static files or dynamic documents")
+    (description
+     "Servr provides an HTTP server in R to serve static files, or dynamic
+documents that can be converted to HTML files (e.g., R Markdown) under a given
+directory.")
+    (license l:expat)))