Fix beta version fetching bug and styling issues

[gerteck]

Overview of changes:

Fixes #272 which was bug due to unnecessary fetch of insertions.html even if there were no <cv-insertion> elements or if it did not exist, as well as a duplicate stylesheet issue to prevent crashes if host page has duplicate link tags.

SEMVER impact of the PR:

• Major (when you make incompatible API changes)
• Minor (when you add functionality in a backward compatible manner)
• Patch (when you make backward compatible bug fixes)

Checklist: ☑️

• Updated the documentation for feature additions and enhancements
• Added tests for bug fixes or features
• Linked all related issues
• No unrelated changes

Merge Instructions:

• For feature branches merging to develop: Prefer Squash and Merge.
• For release/hotfix branches merging to main, or subsequent sync back-merges merging to develop: ONLY use Create a Merge Commit.

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