feature(handler): introduce new elixir handler

lua/gx/handlers/elixir.lua

@@ -0,0 +1,28 @@
+local helper = require("gx.helper")
+
+---@type GxHandler
+local M = {
+  -- every filetype and filename
+  name = "elixir",
+  filetype = { "exs" },
+  filename = nil,
+}
+
+-- hex.pm pattern: https://hex.pm/packages/<package>/<version>
+local hex_url = "https://hex.pm/packages/"
+local pattern = '{:([%l_]*),%s[~>=]-%s"([%d.]*)"[^}]*}'
+
+-- matches package and version from line, e.g. {:dep, ~> "1.0.0"} => "dep", "1.0.0"
+function M.handle(_, line, _)
+  local package_name, version = string.match(line, pattern)
+  package_name = package_name ~= "" and package_name or nil
+  version = version ~= "" and version or nil
+
+  local hex_path = package_name and version and (package_name .. "/" .. version)
+    or package_name
+    or nil
+
+  return hex_path and (hex_url .. hex_path) or nil
+end
+
+return M