fix: define main entry point in package.json

[ozyx]

Closes #7297

Describe your changes:

Define main in package.json so we can import openmct from 'openmct' out of the box!

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• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Is this change backwards compatible? For example, developers won't need to change how they are calling the API or how they've extended core plugins such as Tables or Plots.

Author Checklist

• Changes address original issue?
• Tests included and/or updated with changes?
• Command line build passes?
• Has this been smoke tested?
• Testing instructions included in associated issue OR is this a dependency/testcase change?

Reviewer Checklist

• Changes appear to address issue?
• Reviewer has tested changes by following the provided instructions?
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[deploysentinel]

Current Playwright Test Results Summary

✅ 164 Passing - ⚠️ 1 Flaky

Run may still be in progress, this comment will be updated as current testing workflow or job completes...

(Last updated on 12/14/2023 12:07:44am UTC)

Run Details

Running Job e2e-stable on CircleCI

Commit: c2ddaa2

Started: 12/13/2023 11:56:22pm UTC

⚠️ Flakes

📄   functional/plugins/notebook/notebookSnapshots.e2e.spec.js • 1 Flake

Test Case Results

Test Case	Last 7 days Failures	Last 7 days Flakes
Snapshot image tests Can drop an image onto a notebook and create a new entry Retry 1 • Initial Attempt	0% (0) 0 / 27 runs failed over last 7 days	55.56% (15) 15 / 27 runs flaked over last 7 days

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View Detailed Build Results

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Current Playwright Test Results Summary

✅ 15 Passing - ⚠️ 1 Flaky

Run may still be in progress, this comment will be updated as current testing workflow or job completes...

(Last updated on 12/14/2023 12:07:44am UTC)

Run Details

Running Workflow e2e-couchdb on Github Actions

Commit: c2ddaa2

Started: 12/13/2023 11:55:39pm UTC

⚠️ Flakes

📄   functional/plugins/notebook/notebookWithCouchDB.e2e.spec.js • 1 Flake

Test Case Results

Test Case	Last 7 days Failures	Last 7 days Flakes
Notebook Tests with CouchDB @couchdb Inspect Notebook Entry Network Requests Retry 1 • Initial Attempt	0% (0) 0 / 23 runs failed over last 7 days	8.70% (2) 2 / 23 runs flaked over last 7 days

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View Detailed Build Results

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[codecov]

Codecov Report

Merging #7298 (c2ddaa2) into master (902ed02) will increase coverage by 0.03%.
Report is 1 commits behind head on master.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7298      +/-   ##
==========================================
+ Coverage   55.94%   55.98%   +0.03%     
==========================================
  Files         655      655              
  Lines       26297    26297              
  Branches     2541     2541              
==========================================
+ Hits        14713    14723      +10     
+ Misses      10878    10867      -11     
- Partials      706      707       +1     

Flag	Coverage Δ
e2e-full	41.91% <ø> (+0.06%)	⬆️
e2e-stable	58.44% <ø> (+0.07%)	⬆️
unit	49.26% <ø> (-0.01%)	⬇️

see 5 files with indirect coverage changes

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