docs: Update README Resources section

[ceohockey60]

#9438 # SUMMARY

Updating README Resources section with May 2020 virtual meetup recording and link to Youtube channel

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[codecov-commenter]

Codecov Report

Merging #9864 into master will increase coverage by 4.83%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #9864      +/-   ##
==========================================
+ Coverage   66.33%   71.16%   +4.83%     
==========================================
  Files         588      588              
  Lines       30815    30815              
  Branches     3238     3238              
==========================================
+ Hits        20442    21931    +1489     
+ Misses      10186     8773    -1413     
+ Partials      187      111      -76     

Flag	Coverage Δ
#cypress	53.98% <ø> (?)
#javascript	59.30% <ø> (ø)
#python	71.32% <ø> (+0.03%)	⬆️

Impacted Files	Coverage Δ
superset/sql_lab.py	78.26% <0.00%> (+0.43%)	⬆️
...rontend/src/SqlLab/components/AceEditorWrapper.tsx	56.98% <0.00%> (+1.07%)	⬆️
superset-frontend/src/components/EditableTitle.jsx	81.69% <0.00%> (+1.40%)	⬆️
...perset-frontend/src/components/CopyToClipboard.jsx	36.36% <0.00%> (+1.51%)	⬆️
...hboard/components/resizable/ResizableContainer.jsx	71.87% <0.00%> (+1.56%)	⬆️
superset/result_set.py	98.31% <0.00%> (+1.68%)	⬆️
...ashboard/components/gridComponents/ChartHolder.jsx	81.35% <0.00%> (+1.69%)	⬆️
superset-frontend/src/utils/common.js	69.64% <0.00%> (+1.78%)	⬆️
...src/explore/components/controls/VizTypeControl.jsx	78.84% <0.00%> (+1.92%)	⬆️
superset-frontend/src/explore/controlUtils.js	96.93% <0.00%> (+2.04%)	⬆️
... and 141 more

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