* 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`.