Add note about curl package to http module;

api/init.lua

@@ -984,6 +984,7 @@ return {
       },
       external = true,
       functions = {},
+      notes = "On Linux, this module requires the `curl` library to be installed.  Example on Debian-based distributions:\n\n    sudo apt install libcurl4-openssl-dev",
       objects = {}
     },
     {

api/lovr/http/init.lua

@@ -52,6 +52,12 @@ return {
     - `headers` is a table of response headers.
   ]],
   external = true,
+  notes = [[
+    On Linux, this module requires the `curl` library to be installed.  Example on Debian-based
+    distributions:
+
+        sudo apt install libcurl4-openssl-dev
+  ]],
   example = [[
     local http = require 'http'