egui_extras: Enable setting DatePickerButton start and end year explicitly (#7061)

Add the ability to set the `DatePickerButton`'s start and end years via
new `start_year` and `end_year` methods.

Continue to use the existing today - 100 years and today + 10 years
behavior if a year is not specified.

* This more fully closes <https://github.com/emilk/egui/issues/3597> and
expands on <https://github.com/emilk/egui/pull/3599>.
* [x] I have followed the instructions in the PR template

crates/egui_extras/src/datepicker/button.rs

@@ -1,6 +1,7 @@
 use super::popup::DatePickerPopup;
 use chrono::NaiveDate;
 use egui::{Area, Button, Frame, InnerResponse, Key, Order, RichText, Ui, Widget};
+use std::ops::RangeInclusive;
 
 #[derive(Default, Clone)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
@@ -19,6 +20,7 @@ pub struct DatePickerButton<'a> {
     show_icon: bool,
     format: String,
     highlight_weekends: bool,
+    start_end_years: Option<RangeInclusive<i32>>,
 }
 
 impl<'a> DatePickerButton<'a> {
@@ -33,6 +35,7 @@ impl<'a> DatePickerButton<'a> {
             show_icon: true,
             format: "%Y-%m-%d".to_owned(),
             highlight_weekends: true,
+            start_end_years: None,
         }
     }
 
@@ -101,6 +104,17 @@ impl<'a> DatePickerButton<'a> {
         self.highlight_weekends = highlight_weekends;
         self
     }
+
+    /// Set the start and end years for the date picker. (Default: today's year - 100 to today's year + 10)
+    /// This will limit the years you can choose from in the dropdown to the specified range.
+    ///
+    /// For example, if you want to provide the range of years from 2000 to 2035, you can use:
+    /// `start_end_years(2000..=2035)`.
+    #[inline]
+    pub fn start_end_years(mut self, start_end_years: RangeInclusive<i32>) -> Self {
+        self.start_end_years = Some(start_end_years);
+        self
+    }
 }
 
 impl Widget for DatePickerButton<'_> {
@@ -167,6 +181,7 @@ impl Widget for DatePickerButton<'_> {
                                 calendar: self.calendar,
                                 calendar_week: self.calendar_week,
                                 highlight_weekends: self.highlight_weekends,
+                                start_end_years: self.start_end_years,
                             }
                             .draw(ui)
                         })

crates/egui_extras/src/datepicker/popup.rs

@@ -35,6 +35,7 @@ pub(crate) struct DatePickerPopup<'a> {
     pub calendar: bool,
     pub calendar_week: bool,
     pub highlight_weekends: bool,
+    pub start_end_years: Option<std::ops::RangeInclusive<i32>>,
 }
 
 impl DatePickerPopup<'_> {
@@ -84,7 +85,11 @@ impl DatePickerPopup<'_> {
                                 ComboBox::from_id_salt("date_picker_year")
                                     .selected_text(popup_state.year.to_string())
                                     .show_ui(ui, |ui| {
-                                        for year in today.year() - 100..today.year() + 10 {
+                                        let (start_year, end_year) = match &self.start_end_years {
+                                            Some(range) => (*range.start(), *range.end()),
+                                            None => (today.year() - 100, today.year() + 10),
+                                        };
+                                        for year in start_year..=end_year {
                                             if ui
                                                 .selectable_value(
                                                     &mut popup_state.year,