feat: add what century is it solution

Author: marcode24

codewars/what-century-is-it/README.md

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+# What Century Is It?
+
+## Description
+
+Return the century of the input year. The input will always be a 4 digit string, so there is no need for validation.
+
+Examples
+
+```txt
+"1999" --> "20th"
+"2011" --> "21st"
+"2154" --> "22nd"
+"2259" --> "23rd"
+"1124" --> "12th"
+"2000" --> "20th"
+```

codewars/what-century-is-it/solution.js

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+const whatCentury = (year) => {
+  const suffixRules = [
+    { suffix: 'st', rule: (c) => c % 10 === 1 && c % 100 !== 11 },
+    { suffix: 'nd', rule: (c) => c % 10 === 2 && c % 100 !== 12 },
+    { suffix: 'rd', rule: (c) => c % 10 === 3 && c % 100 !== 13 },
+    { suffix: 'th', rule: () => true },
+  ];
+  const century = Math.ceil(year / 100);
+  const { suffix } = suffixRules.find((rule) => rule.rule(century));
+  return `${century}${suffix}`;
+};
+
+module.exports = whatCentury;

codewars/what-century-is-it/solution.test.js

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+const whatCentury = require('./solution');
+
+describe('What Century Is It', () => {
+  const testCases = [
+    {
+      input: 2023,
+      output: '21st',
+    },
+    {
+      input: 2000,
+      output: '20th',
+    },
+    {
+      input: 1901,
+      output: '20th',
+    },
+    {
+      input: 1899,
+      output: '19th',
+    },
+    {
+      input: '1999',
+      output: '20th',
+    },
+    {
+      input: '2011',
+      output: '21st',
+    },
+    {
+      input: '2154',
+      output: '22nd',
+    },
+    {
+      input: '2259',
+      output: '23rd',
+    },
+    {
+      input: '1234',
+      output: '13th',
+    },
+    {
+      input: '1023',
+      output: '11th',
+    },
+    {
+      input: '2000',
+      output: '20th',
+    },
+  ];
+
+  it('should return a string type', () => {
+    expect(typeof whatCentury(2023)).toBe('string');
+  });
+
+  it.each(testCases)('should return $output', (testCase) => {
+    expect(whatCentury(testCase.input)).toBe(testCase.output);
+  });
+});