test(chore): update ArduinoJson version

[sleepdefic1t]

Proposed changes

This PR updates ArduinoJson v.5.13.2 >> v.6.10.1.

Specifically, this PR does the following:

• updates ArduinoJson submodule.
• updateds PIO.ini ArduinoJson flags (enforce v.6.10.1).
• updates JSON use patterns in tests.
• updates Wallets::Top test case.
• adds ESP8266 & ESP32 WiFi option to test_main.cpp for IoT.
• updates documentation with changes.

Types of changes

• Build (changes that affect the build system)
• Test (adding missing tests or fixing existing tests)

Checklist

• I have read the CONTRIBUTING documentation
• Lint and unit tests pass locally with my changes
• I have added necessary documentation (if appropriate)

Further comments

This PR also resolves failing tests in #85 & #86

[codecov-io]

Codecov Report

Merging #87 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master     #87   +/-   ##
======================================
  Coverage    96.4%   96.4%           
======================================
  Files          14      14           
  Lines         250     250           
======================================
  Hits          241     241           
  Misses          9       9

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 735f820...4255ff0. Read the comment docs.