build: update tests

[VerteDinde]

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.
• The changes are appropriately documented (if applicable).
• The changes have sufficient test coverage (if applicable).
• The testsuite passes successfully on my local machine (if applicable).

Summarize your changes:

Some of the tests here are using older versions of Node and an outdated template for snapcraft.yml. This PR aims to upgrade the node versions and slightly modernize the .yaml so tests pass

NOTE: It looks like the serial tests have been failing consistently on CI, and are also failing locally. Master's last pass date is Dec. of 2020. These need to get back up and running, but is going to take either A) getting Multipass to work in GH Actions or B) a custom image that comes with the needed runners for snapcraft.

[codecov]

Codecov Report

Merging #142 (d822456) into master (7a4a4df) will decrease coverage by 4.34%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##            master     #142      +/-   ##
===========================================
- Coverage   100.00%   95.65%   -4.35%     
===========================================
  Files            8        8              
  Lines          253      253              
===========================================
- Hits           253      242      -11     
- Misses           0       11      +11     

Impacted Files	Coverage Δ
src/snapcraft.js	76.66% <0.00%> (-23.34%)	⬇️
src/hooks.js	92.85% <0.00%> (-7.15%)	⬇️
src/index.js	94.64% <0.00%> (-5.36%)	⬇️

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