docs: Fix a few typos (#606)

* docs: Fix a few typos

There are small typos in:
- doc/versioning.md
- src/components/ble/NimbleController.cpp
- src/libs/mynewt-nimble/CODING_STANDARDS.md
- src/libs/mynewt-nimble/docs/btshell/btshell_GAP.rst
- src/systemtask/SystemTask.cpp

Fixes:
- Should read `milliseconds` rather than `miliseconds`.
- Should read `unnecessary` rather than `uncesseray`.
- Should read `target` rather than `tharget`.
- Should read `project` rather than `projct`.
- Should read `preferred` rather than `prefered`.
- Should read `functioning` rather than `functionning`.
- Should read `forever` rather than `forver`.
- Should read `existing` rather than `exisiting`.

src/systemtask/SystemTask.cpp

@@ -350,7 +350,7 @@ void SystemTask::Work() {
       if (bleDiscoveryTimer == 0) {
         isBleDiscoveryTimerRunning = false;
         // Services discovery is deffered from 3 seconds to avoid the conflicts between the host communicating with the
-        // tharget and vice-versa. I'm not sure if this is the right way to handle this...
+        // target and vice-versa. I'm not sure if this is the right way to handle this...
         nimbleController.StartDiscovery();
       } else {
         bleDiscoveryTimer--;