fixed numerical sorting on HTML report

[agshumate]

The columns in the typing rate table and the thresholds table were sorting lexicographically. I updated the tables to sort these columns numerically. Fixes #155

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• [x] Changes are clearly described above
• [x] Any relevant issue threads are referenced in the description
• ~[ ] Any new features are tested (see the development manual for details)~
• [x] CLI documentation (see docs/cli.md) and Python API documentation (see microhapulator/api.py) are up-to-date and in sync
• ~[ ] Substantial changes are documented in CHANGELOG.md (see https://keepachangelog.com/en/1.0.0/)~