docs: code samples modernized

docs/getting_started/look_and_feel.md

@@ -69,8 +69,10 @@ performed without sacrificing accuracy. Please see the below example for a quick
 === "C++ modules"
 
     ```cpp
+    #include <format>
     #include <iomanip>
     #include <iostream>
+    #include <print>
     import mp_units;
 
     using namespace mp_units;
@@ -97,10 +99,10 @@ performed without sacrificing accuracy. Please see the below example for a quick
       std::cout << v1 << '\n';                                        // 110 km/h
       std::cout << std::setw(10) << std::setfill('*') << v2 << '\n';  // ***70 mi/h
       std::cout << std::format("{:*^10}\n", v3);                      // *110 km/h*
-      std::cout << std::format("{:%N in %U}\n", v4);                  // 70 in mi/h
-      std::cout << std::format("{:{%N:.2f}%?%U}\n", v5);              // 30.56 in m/s
-      std::cout << std::format("{:{%N:.2f}%?{%U:n}}\n", v6);          // 31.29 in m s⁻¹
-      std::cout << std::format("{:%N}\n", v7);                        // 31
+      std::println("{:%N in %U}", v4);                                // 70 in mi/h
+      std::println("{:{%N:.2f}%?%U}", v5);                            // 30.56 m/s
+      std::println("{:{%N:.2f}%?{%U:n}}", v6);                        // 31.29 m s⁻¹
+      std::println("{:%N}", v7);                                      // 31
     }
     ```
 
@@ -112,8 +114,10 @@ performed without sacrificing accuracy. Please see the below example for a quick
     #include <mp-units/systems/international/international.h>
     #include <mp-units/systems/isq/isq.h>
     #include <mp-units/systems/si/si.h>
+    #include <format>
     #include <iomanip>
     #include <iostream>
+    #include <print>
 
     using namespace mp_units;
 
@@ -139,14 +143,14 @@ performed without sacrificing accuracy. Please see the below example for a quick
       std::cout << v1 << '\n';                                        // 110 km/h
       std::cout << std::setw(10) << std::setfill('*') << v2 << '\n';  // ***70 mi/h
       std::cout << std::format("{:*^10}\n", v3);                      // *110 km/h*
-      std::cout << std::format("{:%N in %U}\n", v4);                  // 70 in mi/h
-      std::cout << std::format("{:{%N:.2f}%?%U}\n", v5);              // 30.56 in m/s
-      std::cout << std::format("{:{%N:.2f}%?{%U:n}}\n", v6);          // 31.29 in m s⁻¹
-      std::cout << std::format("{:%N}\n", v7);                        // 31
+      std::println("{:%N in %U}", v4);                                // 70 in mi/h
+      std::println("{:{%N:.2f}%?%U}", v5);                            // 30.56 m/s
+      std::println("{:{%N:.2f}%?{%U:n}}", v6);                        // 31.29 m s⁻¹
+      std::println("{:%N}", v7);                                      // 31
     }
     ```
 
-!!! example "[Try it on Compiler Explorer](https://godbolt.org/z/Tsesa1Pvq)"
+!!! example "[Try it on Compiler Explorer](https://godbolt.org/z/hWzxf1j1M)"
 
 !!! note
 

docs/getting_started/quick_start.md

@@ -149,7 +149,7 @@ This introduces an additional type-safety.
 === "C++ modules"
 
     ```cpp
-    #include <iostream>
+    #include <print>
     import mp_units;
 
     int main()
@@ -157,32 +157,32 @@ This introduces an additional type-safety.
       using namespace mp_units;
       using namespace mp_units::si::unit_symbols;
       using namespace mp_units::usc::unit_symbols;
-
+    
       quantity_point temp{20. * deg_C};
-      std::cout << "Temperature: "
-                  << temp.quantity_from_zero() << " ("
-                  << temp.in(deg_F).quantity_from_zero() << ")\n";
+      std::println("Temperature: {} ({})",
+                   temp.quantity_from_zero(),
+                   temp.in(deg_F).quantity_from_zero());
     }
     ```
 
 === "Header files"
 
     ```cpp
-    #include <mp-units/ostream.h>
+    #include <mp-units/format.h>
     #include <mp-units/systems/si/si.h>
     #include <mp-units/systems/usc/usc.h>
-    #include <iostream>
-
+    #include <print>
+    
     int main()
     {
       using namespace mp_units;
       using namespace mp_units::si::unit_symbols;
       using namespace mp_units::usc::unit_symbols;
-
+    
       quantity_point temp{20. * deg_C};
-      std::cout << "Temperature: "
-                  << temp.quantity_from_zero() << " ("
-                  << temp.in(deg_F).quantity_from_zero() << ")\n";
+      std::println("Temperature: {} ({})",
+                   temp.quantity_from_zero(),
+                   temp.in(deg_F).quantity_from_zero());
     }
     ```