[Documentation] Add Glossary Mark Down

[gerickson]

Documentation issues

There are a number of acronyms and terms that a product or platform integrator new to Matter is likely to encounter that are difficult to determine the meaning of without access to the specification. While the specification is available, it shouldn't be necessary to work with the Matter project repository source code.

Toward that end, I am proposing the creation of a doc/GLOSSARY.md markdown document with the initial following content:

This defines acronyms and terminology frequently mentioned and used
throughout the Matter project repository that are not otherwise well
defined before their use and introduction absent the Matter
specification.

**Check-In Protocol**
: A specific protocol used by a _Long Interval Time_ (LIT)
_Intermittently Connected Device_ (ICD) to notify the client device that
they are temporarily available for communication.

**CIP**
: Check-In Protocol

**Electric Vehicle Supply Equipment**
: The hardware and software that safely delivers electricity from the
grid to an electric vehicle's battery, essentially the "charging
station" with its connectors, cables, and communication systems that
manage power flow and ensure safety during the charging process.

**EVSE**
:Electric Vehicle Supply Equipment

**ICD**
: Intermittently Connected Device

**Intermittently Connected Device**
: A device that enters a low-power sleep mode for periods of time to
conserve battery life, and thus is not always reachable on the
network.

**LIT**
: Long Interval Time

**Long Interval Time**
: A configuration for an _Intermittently Connected Device_ (ICD) where
the device sleeps for much longer intervals (that is, minutes or even
hours).

**Short Interval Time**
: A configuration for an _Intermittently Connected Device_ (ICD) where
the device's polling interval is relatively short (that is, several
seconds).

**SIT**
: Short Interval Time

**UAT**
: User Active Mode Trigger

**User Active Mode Trigger**
: A feature used by an _Intermittently Connected Device_ (ICD) that
allows a user interaction (like pressing a button on a device) to
immediately switch the ICD from Idle mode to Active mode, making it
instantly responsive for a short period of time.

GLOSSARY.md

Platform

No response

Anything else?

No response