Make example binaries proper cargo examples (#7019)

Should not be built by default with `cargo build`
Instead are compiled with `cargo test` to avoid bitrot
Run with `cargo run -p ... --example ...`

crates/nu-table/examples/demo.rs

@@ -0,0 +1,107 @@
+use nu_protocol::Config;
+use nu_table::{Alignments, Table, TableTheme, TextStyle};
+use std::collections::HashMap;
+use tabled::papergrid::records::{cell_info::CellInfo, tcell::TCell};
+
+fn main() {
+    let args: Vec<_> = std::env::args().collect();
+    let mut width = 0;
+
+    if args.len() > 1 {
+        // Width in terminal characters
+        width = args[1].parse::<usize>().expect("Need a width in columns");
+    }
+
+    if width < 4 {
+        println!("Width must be greater than or equal to 4, setting width to 80");
+        width = 80;
+    }
+
+    // The mocked up table data
+    let (table_headers, row_data) = make_table_data();
+    // The table headers
+    let headers = vec_of_str_to_vec_of_styledstr(&table_headers, true);
+    // The table rows
+    let rows = vec_of_str_to_vec_of_styledstr(&row_data, false);
+    // The table itself
+    let count_cols = std::cmp::max(rows.len(), headers.len());
+    let mut rows = vec![rows; 3];
+    rows.insert(0, headers);
+    let table = Table::new(rows, (3, count_cols), width, true, false);
+    // FIXME: Config isn't available from here so just put these here to compile
+    let color_hm: HashMap<String, nu_ansi_term::Style> = HashMap::new();
+    // get the default config
+    let config = Config::default();
+    // Capture the table as a string
+    let output_table = table
+        .draw_table(
+            &config,
+            &color_hm,
+            Alignments::default(),
+            &TableTheme::rounded(),
+            width,
+        )
+        .unwrap_or_else(|| format!("Couldn't fit table into {} columns!", width));
+    // Draw the table
+    println!("{}", output_table)
+}
+
+fn make_table_data() -> (Vec<&'static str>, Vec<&'static str>) {
+    let table_headers = vec![
+        "category",
+        "description",
+        "emoji",
+        "ios_version",
+        "unicode_version",
+        "aliases",
+        "tags",
+        "category2",
+        "description2",
+        "emoji2",
+        "ios_version2",
+        "unicode_version2",
+        "aliases2",
+        "tags2",
+    ];
+
+    let row_data = vec![
+        "Smileys & Emotion",
+        "grinning face",
+        "😀",
+        "6",
+        "6.1",
+        "grinning",
+        "smile",
+        "Smileys & Emotion",
+        "grinning face",
+        "😀",
+        "6",
+        "6.1",
+        "grinning",
+        "smile",
+    ];
+
+    (table_headers, row_data)
+}
+
+fn vec_of_str_to_vec_of_styledstr(
+    data: &[&str],
+    is_header: bool,
+) -> Vec<TCell<CellInfo<'static>, TextStyle>> {
+    let mut v = vec![];
+
+    for x in data {
+        if is_header {
+            v.push(Table::create_cell(
+                String::from(*x),
+                TextStyle::default_header(),
+            ))
+        } else {
+            v.push(Table::create_cell(
+                String::from(*x),
+                TextStyle::basic_left(),
+            ))
+        }
+    }
+    v
+}