themes: Add theme.toml for the Apertis theme

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

themes/apertis/theme.toml

+name = "Apertis"
+license = "MIT"
+licenselink = "https://gitlab.apertis.org/docs/apertis-website/-/blob/master/themes/apertis/LICENSE"
+description = "The theme for apertis.org, based on Beautiful Hugo"
+tags = ["company", "portfolio", "projects", "minimal", "responsive"]
+features = ["responsive"]
+min_version = 0.17
+
+[author]
+    name = "Jon Wallace"
+    homepage = "https://www.jonwallacedesign.com/"