refactor: knot unit helper renamed to kn in FPS

Relates to #357

example/aliases/foot_pound_second.cpp

@@ -68,7 +68,7 @@ void print_details(std::string_view description, const Ship& ship)
             << STD_FMT::format("{:20} : {}\n", "beam", fmt_line<si::fps::length::yd<>, si::length::m<>>(ship.beam))
             << STD_FMT::format("{:20} : {}\n", "mass", fmt_line<si::fps::mass::lton<>, si::mass::t<>>(ship.mass))
             << STD_FMT::format("{:20} : {}\n", "speed",
-                               fmt_line<si::fps::speed::knot<>, si::speed::km_per_h<>>(ship.speed))
+                               fmt_line<si::fps::speed::kn<>, si::speed::km_per_h<>>(ship.speed))
             << STD_FMT::format("{:20} : {}\n", "power", fmt_line<si::fps::power::hp<>, si::power::kW<>>(ship.power))
             << STD_FMT::format("{:20} : {}\n", "main guns",
                                fmt_line<si::fps::length::in<>, si::length::mm<>>(ship.mainGuns))
@@ -101,7 +101,7 @@ int main()
   auto iowa = Ship{.length{ft<>(860.)},
                    .draft{ft<>(37.) + in<>(2.)},
                    .beam{ft<>(108.) + in<>(2.)},
-                   .speed{knot<>(33)},
+                   .speed{kn<>(33)},
                    .mass{lton<>(57'540)},
                    .mainGuns{in<>(16)},
                    .shellMass{lb<>(2700)},
@@ -112,7 +112,7 @@ int main()
   auto kgv = Ship{.length{ft<>(745.1)},
                   .draft{ft<>(33.) + in<>(7.5)},
                   .beam{ft<>(103.2) + in<>(2.5)},
-                  .speed{knot<>(28.3)},
+                  .speed{kn<>(28.3)},
                   .mass{lton<>(42'245)},
                   .mainGuns{in<>(14)},
                   .shellMass{lb<>(1'590)},

example/literals/foot_pound_second.cpp

@@ -108,7 +108,7 @@ int main()
   auto iowa = Ship{.length{860._q_ft},
                    .draft{37._q_ft + 2._q_in},
                    .beam{108._q_ft + 2._q_in},
-                   .speed{33_q_knot},
+                   .speed{33_q_kn},
                    .mass{57'540_q_lton},
                    .mainGuns{16_q_in},
                    .shellMass{2700_q_lb},
@@ -119,7 +119,7 @@ int main()
   auto kgv = Ship{.length{745.1_q_ft},
                   .draft{33._q_ft + 7.5_q_in},
                   .beam{103.2_q_ft + 2.5_q_in},
-                  .speed{28.3_q_knot},
+                  .speed{28.3_q_kn},
                   .mass{42'245_q_lton},
                   .mainGuns{14_q_in},
                   .shellMass{1'590_q_lb},

example/references/foot_pound_second.cpp

@@ -112,7 +112,7 @@ int main()
   auto iowa = Ship{.length{860. * ft},
                    .draft{37. * ft + 2. * in},
                    .beam{108. * ft + 2. * in},
-                   .speed{33 * knot},
+                   .speed{33 * kn},
                    .mass{57'540 * lton},
                    .mainGuns{16 * in},
                    .shellMass{2700 * lb},
@@ -123,7 +123,7 @@ int main()
   auto kgv = Ship{.length{745.1 * ft},
                   .draft{33. * ft + 7.5 * in},
                   .beam{103.2 * ft + 2.5 * in},
-                  .speed{28.3 * knot},
+                  .speed{28.3 * kn},
                   .mass{42'245 * lton},
                   .mainGuns{14 * in},
                   .shellMass{1'590 * lb},