[gnome-calculator] Added a function to convert frequencies from one to another unit.

[Robert Roth <robertroth src gnome org>]

commit 0b98fcb377d33c57dad11a5791639eb36045b63e
Author: dave90dave <dave hulst gmail com>
Date:   Sun Jan 31 16:48:51 2021 +0100

    Added a function to convert frequencies from one to another unit.
    
    There are new conversion units added to convert Frequencies (visable in the keyboard mode).
    
    You can now convert every unit between:
    - Hertz
    - Kilohertz
    - Megahertz
    - Gigahertz
    - Terahertz

 lib/unit.vala | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/lib/unit.vala b/lib/unit.vala
index 5e62f66c..68ff836c 100644
--- a/lib/unit.vala
+++ b/lib/unit.vala
@@ -33,6 +33,7 @@ public class UnitManager : Object
         var volume_category = default_unit_manager.add_category ("volume", _("Volume"));
         var weight_category = default_unit_manager.add_category ("weight", _("Mass"));
         var duration_category = default_unit_manager.add_category ("duration", _("Duration"));
+        var frequency_category = default_unit_manager.add_category ("frequency", _("Frequency"));
         var temperature_category = default_unit_manager.add_category ("temperature", _("Temperature"));
         var digitalstorage_category = default_unit_manager.add_category ("digitalstorage", _("Digital 
Storage"));
 
@@ -132,6 +133,11 @@ public class UnitManager : Object
         digitalstorage_category.add_unit (new Unit ("yottabyte", _("Yottabytes"), dpgettext2 (null, 
"unit-format", "%s YB"), "1000000000000000000000000x", "x/1000000000000000000000000", dpgettext2 (null, 
"unit-symbols", "yottabyte,yottabytes,YB")));
         digitalstorage_category.add_unit (new Unit ("yobibit", _("Yobibits"), dpgettext2 (null, 
"unit-format", "%s Yib"), "1208925819614629174706176x/8", "8x/1208925819614629174706176", dpgettext2 (null, 
"unit-symbols", "yobibit,yobibits,Yib")));
         digitalstorage_category.add_unit (new Unit ("yobibyte", _("Yobibytes"), dpgettext2 (null, 
"unit-format", "%s YiB"), "1208925819614629174706176x", "x/1208925819614629174706176", dpgettext2 (null, 
"unit-symbols", "yobibyte,yobibytes,YiB")));
+        frequency_category.add_unit (new Unit ("hertz", _("Hertz"), dpgettext2 (null, "unit-format", "%s 
Hz"), "x", "x", dpgettext2 (null, "unit-symbols", "hertz,Hz")));
+        frequency_category.add_unit (new Unit ("kilohertz", _("Kilohertz"), dpgettext2 (null, "unit-format", 
"%s kHz"), "1000x", "x/1000", dpgettext2 (null, "unit-symbols", "kilohertz,kHZ")));
+        frequency_category.add_unit (new Unit ("megahertz", _("Megahertz"), dpgettext2 (null, "unit-format", 
"%s MHz"), "1000000x", "x/1000000", dpgettext2 (null, "unit-symbols", "megahertz,MHz")));
+        frequency_category.add_unit (new Unit ("gigahertz", _("Gigahertz"), dpgettext2 (null, "unit-format", 
"%s GHz"), "1000000000x", "x/1000000000", dpgettext2 (null, "unit-symbols", "gigahertz,GHz")));
+        frequency_category.add_unit (new Unit ("terahertz", _("Terahertz"), dpgettext2 (null, "unit-format", 
"%s THz"), "1000000000000x", "x/1000000000000" ,dpgettext2 (null, "unit-symbols", "terahertz,THz")));
 
         var currency_category = default_unit_manager.add_category ("currency", _("Currency"));
         var currencies = CurrencyManager.get_default ().get_currencies ();