feat: add an about command (#2)

### Explanation

_No response_

### Issue

_No response_

### Attestations

- [x] I have read and agree to the [Code of Conduct](https://docs.nhcarrigan.com/community/coc/)
- [x] I have read and agree to the [Community Guidelines](https://docs.nhcarrigan.com/community/guide/).
- [x] My contribution complies with the [Contributor Covenant](https://docs.nhcarrigan.com/dev/covenant/).

### Dependencies

- [x] I have pinned the dependencies to a specific patch version.

### Style

- [x] I have run the linter and resolved any errors.
- [x] My pull request uses an appropriate title, matching the conventional commit standards.
- [x] My scope of feat/fix/chore/etc. correctly matches the nature of changes in my pull request.

### Tests

- [ ] My contribution adds new code, and I have added tests to cover it.
- [ ] My contribution modifies existing code, and I have updated the tests to reflect these changes.
- [x] All new and existing tests pass locally with my changes.
- [x] Code coverage remains at or above the configured threshold.

### Documentation

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### Versioning

Minor - My pull request introduces a new non-breaking feature.

Reviewed-on: #2
Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Co-committed-by: Naomi Carrigan <commits@nhcarrigan.com>

src/utils/i18n.ts

@@ -3,25 +3,58 @@
  * @license Naomi's Public License
  * @author Naomi Carrigan
  */
+/* eslint-disable @typescript-eslint/no-non-null-assertion -- We've already asserted the language exists through our typeguard.*/
+/* eslint-disable unicorn/no-array-reduce -- It's a clean approach here and makes sense. */
+/* eslint-disable @typescript-eslint/consistent-type-assertions  -- We have likely over-engineered the hell out of this...*/
 
 import { responses } from "../i18n/responses.js";
 
+const isTranslatedLocale = (
+  locale: string,
+): locale is keyof typeof responses => {
+  return locale in responses;
+};
+
 /**
  * Translates a key to the specified locale, performing
  * interpolation on the string.
  * @param key -- The key to translate.
- * @param locale -- The user's locale.
+ * @param rawLocale -- The user's locale.
  * @param interpolation -- An object of keys to replace with values.
  * @returns The translated string.
  */
 export const i18n = (
-  key: keyof (typeof responses)["en"],
-  locale: string,
+  key:
+    | keyof (typeof responses)["en"]
+    | `embed.${keyof (typeof responses)["en"]["embed"]}`
+    | `button.${keyof (typeof responses)["en"]["button"]}`,
+  rawLocale: string,
   interpolation: Record<string, unknown> = {},
 ): string => {
-  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion -- We know the en key exists, but having the loose type helps.
-  const string = responses[locale]?.[key] ?? responses.en![key];
-  // eslint-disable-next-line unicorn/no-array-reduce -- This is the cleanest way to do it, really.
+  const locale: keyof typeof responses = isTranslatedLocale(rawLocale)
+    ? rawLocale
+    : "en";
+  const isNestedProperty = key.startsWith("embed.")
+  || key.startsWith("button.");
+  if (isNestedProperty) {
+    const [ category, property ] = key.split(".") as
+      | ["embed", keyof (typeof responses)["en"]["embed"]]
+      | ["button", keyof (typeof responses)["en"]["button"]];
+    if (category === "embed") {
+      const string = responses[locale]![category][property];
+      return Object.entries(interpolation).reduce((accumulator, [ k, v ]) => {
+        return accumulator.replace(`{{${k}}}`, String(v));
+      }, string);
+    }
+    const string = responses[locale]![category][property];
+    return Object.entries(interpolation).reduce((accumulator, [ k, v ]) => {
+      return accumulator.replace(`{{${k}}}`, String(v));
+    }, string);
+  }
+  const string
+    = responses[locale]![
+      key as Exclude<keyof (typeof responses)["en"], "embed" | "button">
+    ];
   return Object.entries(interpolation).reduce((accumulator, [ k, v ]) => {
     return accumulator.replace(`{{${k}}}`, String(v));
   }, string);