Explicitly add MIT license

[jamesdabbs]

Per discussion in #116, I believe the intent was always for the
viewer code to match license with @pi-base/core, and that the
lack of license in this repo was just an oversight.

[netlify]

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[codecov]

Codecov Report

Merging #117 (be3ae42) into main (908639e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #117   +/-   ##
=======================================
  Coverage   43.16%   43.16%           
=======================================
  Files          25       25           
  Lines         505      505           
  Branches      126      126           
=======================================
  Hits          218      218           
  Misses        287      287           

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[cypress]

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Test summary

14 • 1 • 4 • 0

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Run details

Project	viewer
Status	Failed
Commit	d48df38 ℹ️
Started	Oct 17, 2021 7:08 PM
Ended	Oct 17, 2021 7:10 PM
Duration	02:09 💡
OS	Linux Ubuntu - 20.04
Browser	Electron 91

View run in Cypress Dashboard ➡️

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Failures

	cypress/integration/space.search.spec.ts		1
1	uses suggestions to search by properties

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