Add BLE FS docs link to BLE docs

Author: Elara6331

doc/ble.md

@@ -9,6 +9,7 @@ This page describes the BLE implementation and API built in this firmware.
 ### Table of Contents
 
 - [BLE Connection](#ble-connection)
+- [BLE FS](#ble-fs)
 - [BLE UUIDs](#ble-uuids)
 - [BLE Services](#ble-services)
   - [CTS](#cts)
@@ -51,6 +52,13 @@ If **CTS** is detected, it'll request the current time to the companion applicat
 
 ---
 
+## BLE FS
+
+The documentation for BLE FS can be found here:
+[BLEFS.md](./BLEFS.md)
+
+---
+
 ## BLE UUIDs
 When possible, InfiniTime tries to implement BLE services defined by the BLE specification. 
 
@@ -285,4 +293,4 @@ This characteristic expects a particular format:
 - Microsecond divided by `1e6*256` (`uint8`)
 - Binary 0001 (`uint8`)
 
-Write all of these together, encoded as little-endian, to the current time characteristic.
+Write all of these together, encoded as little-endian, to the current time characteristic.