Add sounds README and alarm

sounds/README.md

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+# Sounds
+## Sources and Credit
+ * `announcement_4-tone_up.ogg`
+   * Source: [freesound.org](https://freesound.org/people/kwahmah_02/sounds/245956/)
+ * `announcement_4-tone_up_smooth.ogg`, `announcement_4-tone_up_quickest.ogg`, `announcement_4-tone_up_smooth_quick.ogg`
+   * Source: [freesound.org](https://freesound.org/people/chimerical/sounds/105228/)
+ * `alarm_simple.ogg`
+   * Source: [freesound.org](https://freesound.org/people/Suburbanwizard/sounds/440307/)
+