Add design note for UI Module#24

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HiroyasuNishiyama wants to merge 3 commits intonode-red:masterfrom

node-red-hitachi:ui-module

Commits on Feb 10, 2020

add design note for UI Module
HiroyasuNishiyama
committed

Commits on Aug 18, 2020

update design note for UI Module
KazuhiroItoh
committed

Commits on Dec 14, 2020

Added about the required Node-RED additional function
KazuhiroItoh
committed