Update node version requirements for v10 to v12

[derrickmehaffy]

Signed-off-by: Derrick Mehaffy derrickmehaffy@gmail.com

Description of what you did:

As Strapi does not support Node v13/v14 I've updated all the requirements and made a few notes in the Documentation as well as the README.md and changed all of the packages to reference the node engine based on: https://docs.npmjs.com/files/package.json#engines

@alexandrebodin I am submitting this into the documentation branch but this will also need to be merged into master to update all the package node engine versions (after we test with things like Heroku which do use that engine version)

[codecov]

Codecov Report

Merging #7409 into documentation will increase coverage by 7.03%.
The diff coverage is n/a.

@@                Coverage Diff                @@
##           documentation    #7409      +/-   ##
=================================================
+ Coverage          19.14%   26.17%   +7.03%     
=================================================
  Files                855     1130     +275     
  Lines              11933    15414    +3481     
  Branches            1898     2439     +541     
=================================================
+ Hits                2284     4034    +1750     
- Misses              8100     9561    +1461     
- Partials            1549     1819     +270     

Flag	Coverage Δ
#front	18.27% <ø> (+3.78%)	⬆️
#unit	52.96% <ø> (+13.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/strapi-plugin-email/admin/src/pluginId.js	0.00% <0.00%> (-100.00%)	⬇️
...n/src/containers/NotificationProvider/constants.js	0.00% <0.00%> (-100.00%)	⬇️
...i-admin/admin/src/containers/SettingsPage/index.js	0.00% <0.00%> (-66.67%)	⬇️
...trapi-admin/admin/src/containers/LeftMenu/index.js	5.00% <0.00%> (-61.67%)	⬇️
...n/admin/src/containers/LanguageProvider/reducer.js	0.00% <0.00%> (-61.54%)	⬇️
...in/admin/src/containers/Webhooks/ListView/index.js	0.00% <0.00%> (-42.11%)	⬇️
...in/admin/src/containers/Webhooks/EditView/index.js	0.00% <0.00%> (-38.40%)	⬇️
packages/strapi/lib/services/metrics/index.js	65.00% <0.00%> (-35.00%)	⬇️
...admin/admin/src/components/ContainerFluid/index.js	66.66% <0.00%> (-33.34%)	⬇️
...s/strapi-admin/admin/src/containers/Admin/index.js	63.82% <0.00%> (-15.66%)	⬇️
... and 645 more

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[alexandrebodin]

I think it supports node v14 now. Need to do a test with travis

[derrickmehaffy]

I don't believe sharp has updated their binaries they ship which is where I see most of the issues. -> libvips which is used by sharp

[alexandrebodin]

LGTM

[derrickmehaffy]

@alexandrebodin @petersg83 @lauriejim

Whoever does the next release, make sure this gets pulled into the master as well, as it updates all the packages package.json as well as the main README.md