Add ale.has to mirror ale#Has in Lua

test/lua/ale_has_spec.lua

@@ -0,0 +1,27 @@
+local eq = assert.are.same
+local ale = require("ale")
+
+describe("ale.has", function()
+    setup(function()
+        _G.vim = {
+            fn = {
+                ["ale#Has"] = function(feature)
+                    if feature == "ale-4.0.0" then
+                        return 1
+                    end
+
+                    return 0
+                end,
+            },
+        }
+    end)
+
+    teardown(function()
+        _G.vim = nil
+    end)
+
+    it("should return valuse from ale#Has correctly", function()
+        eq(true, ale.has("ale-4.0.0"))
+        eq(false, ale.has("ale-20.0.0"))
+    end)
+end)