LibJS: Mark getters of more Temporal objects [[nodiscard]]

PlainDate, PlainTime, and PlainDateTime already do this. All the others
should as well.

Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h

@@ -20,7 +20,7 @@ public:
     Calendar(String identifier, Object& prototype);
     virtual ~Calendar() override = default;
 
-    String const& identifier() const { return m_identifier; }
+    [[nodiscard]] String const& identifier() const { return m_identifier; }
 
 private:
     // 12.5 Properties of Temporal.Calendar Instances, https://tc39.es/proposal-temporal/#sec-properties-of-temporal-calendar-instances

Userland/Libraries/LibJS/Runtime/Temporal/Duration.h

@@ -18,16 +18,16 @@ public:
     Duration(double years, double months, double weeks, double days, double hours, double minutes, double seconds, double milliseconds, double microseconds, double nanoseconds, Object& prototype);
     virtual ~Duration() override = default;
 
-    double years() const { return m_years; }
-    double months() const { return m_months; }
-    double weeks() const { return m_weeks; }
-    double days() const { return m_days; }
-    double hours() const { return m_hours; }
-    double minutes() const { return m_minutes; }
-    double seconds() const { return m_seconds; }
-    double milliseconds() const { return m_milliseconds; }
-    double microseconds() const { return m_microseconds; }
-    double nanoseconds() const { return m_nanoseconds; }
+    [[nodiscard]] double years() const { return m_years; }
+    [[nodiscard]] double months() const { return m_months; }
+    [[nodiscard]] double weeks() const { return m_weeks; }
+    [[nodiscard]] double days() const { return m_days; }
+    [[nodiscard]] double hours() const { return m_hours; }
+    [[nodiscard]] double minutes() const { return m_minutes; }
+    [[nodiscard]] double seconds() const { return m_seconds; }
+    [[nodiscard]] double milliseconds() const { return m_milliseconds; }
+    [[nodiscard]] double microseconds() const { return m_microseconds; }
+    [[nodiscard]] double nanoseconds() const { return m_nanoseconds; }
 
 private:
     // 7.4 Properties of Temporal.Duration Instances, https://tc39.es/proposal-temporal/#sec-properties-of-temporal-duration-instances

Userland/Libraries/LibJS/Runtime/Temporal/Instant.h

@@ -20,7 +20,7 @@ public:
     Instant(BigInt& nanoseconds, Object& prototype);
     virtual ~Instant() override = default;
 
-    BigInt const& nanoseconds() const { return m_nanoseconds; }
+    [[nodiscard]] BigInt const& nanoseconds() const { return m_nanoseconds; }
 
 private:
     virtual void visit_edges(Visitor&) override;

Userland/Libraries/LibJS/Runtime/Temporal/TimeZone.h

@@ -22,8 +22,8 @@ public:
     TimeZone(String identifier, Object& prototype);
     virtual ~TimeZone() override = default;
 
-    String const& identifier() const { return m_identifier; }
-    Optional<OffsetType> const& offset_nanoseconds() const { return m_offset_nanoseconds; }
+    [[nodiscard]] String const& identifier() const { return m_identifier; }
+    [[nodiscard]] Optional<OffsetType> const& offset_nanoseconds() const { return m_offset_nanoseconds; }
     void set_offset_nanoseconds(OffsetType offset_nanoseconds) { m_offset_nanoseconds = offset_nanoseconds; };
 
 private:

Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.h

@@ -18,12 +18,12 @@ public:
     ZonedDateTime(BigInt& nanoseconds, Object& time_zone, Object& calendar, Object& prototype);
     virtual ~ZonedDateTime() override = default;
 
-    BigInt const& nanoseconds() const { return m_nanoseconds; }
-    BigInt& nanoseconds() { return m_nanoseconds; }
-    Object const& time_zone() const { return m_time_zone; }
-    Object& time_zone() { return m_time_zone; }
-    Object const& calendar() const { return m_calendar; }
-    Object& calendar() { return m_calendar; }
+    [[nodiscard]] BigInt const& nanoseconds() const { return m_nanoseconds; }
+    [[nodiscard]] BigInt& nanoseconds() { return m_nanoseconds; }
+    [[nodiscard]] Object const& time_zone() const { return m_time_zone; }
+    [[nodiscard]] Object& time_zone() { return m_time_zone; }
+    [[nodiscard]] Object const& calendar() const { return m_calendar; }
+    [[nodiscard]] Object& calendar() { return m_calendar; }
 
 private:
     virtual void visit_edges(Visitor&) override;