langswitcher.hreflang.html.twig displays incorrect urls when Grav is configured to generate absolute urls

I have configure Grav to generate absolute urls (`absolute_urls: true`). In this case the template langswitcher.hreflang.html.twig displays incorrect urls with duplicate base (e.g. http://www.example.comhttp://www.example.com/en/example).

As a solution, `uri.base` should be added to the url only if `absolute_urls` is set to false:

```
{% if config.system.absolute_urls %}
{% set href_url = lang_url ~ uri.params ~ (uri.query|length > 1 ? '?' ~ uri.query) %}
{% else %}
{% set href_url = uri.base ~ lang_url ~ uri.params ~ (uri.query|length > 1 ? '?' ~ uri.query) %}
{% endif %}
```

Furthermore there is an error in line 12: `config.languages.include_default_lang` doesn't exist and should be replaced by `config.system.languages.include_default_lang`.

Start with langswitcher.hreflang.html.twig, focusing on the href construction and the include_default_lang reference described in the issue. Verify generated links with absolute_urls enabled and disabled, and confirm the language setting is read from the stated system configuration path; done means no duplicate base URL and correct language links in both modes.

Written by the indexing model from the issue text.