Added MyXQL adapter to config template

[bfolkens]

Currently, the configuration doesn't detect the "mysql" type when the MyXQL Ecto adapter is used, leading to the following error:

** (FunctionClauseError) no function clause matching in Mix.Tasks.Giza.Sphinx.Config.generate_source/1

    The following arguments were given to Mix.Tasks.Giza.Sphinx.Config.generate_source/1:

        # 1
        %{database: "db", hostname: "127.0.0.1", password: "", username: "root"}

    Attempted function clauses (showing 1 out of 1):

        defp generate_source(%{type: type, database: database, username: username, password: password, hostname: hostname})

    lib/mix/giza.sphinx.config.ex:42: Mix.Tasks.Giza.Sphinx.Config.generate_source/1
    lib/mix/giza.sphinx.config.ex:20: Mix.Tasks.Giza.Sphinx.Config.run/1
    (mix 1.10.3) lib/mix/task.ex:330: Mix.Task.run_task/3
    (mix 1.10.3) lib/mix/cli.ex:82: Mix.CLI.run_task/2

This patch adds a line to the matching portion of the Mix task to detect the type when the MyXQL adapter is used.