Add Highcharts and map examples for testing and demonstrations

[aidanbruneel]

Summary

Create a maintained, public-facing collection of example Highcharts and map cases that IMAGE developers can use for:

• Manual developer testing
• Investigating supported and unsupported cases
• Demonstrations and presentations
• Identifying useful future test fixtures

Existing and similar examples are currently spread across older issues, comments, and individual lists. They should have a clear canonical location in the repository.

Proposed documentation location

Add component-specific example sectoins in IMAGE-server README.md files:

• handlers/high-charts/README.md or a more suitable README.md file.
• preprocessors/openstreetmap/README.md or a more suitable README.md file.

These sections should remain useful to external contributors and project partners rather than being written only for the internal McGill team.

Information to include

For each example, include as applicable:

• Example name
• Source or webpage
• Chart, map, or scenario type
• What the example is intended to test (if applicable)
• Date the example was last verified

For map examples, include coordinates, location information, or other reproducible inputs when a webpage link alone is insufficient.

Link maintenance

These sections should state that external examples are maintained on a best-effort basis. Third-party webpages may change or disappear, so a broken example does not necessarily indicate a regression in IMAGE.

The examples should be reviewed when related Highcharts or map functionality is substantially changed.

Existing material

If applicable, please review and consolidate any relevant examples from:

• Charts: Decide on supported web chart data formats, e.g. Plotly #129
• STORY: As an IMAGE user, I want to experience a broader variety of chart types, so that I can have a rich IMAGE experience of more chart content on the web. #805

Acceptance criteria

• Existing example links from Charts: Decide on supported web chart data formats, e.g. Plotly #129, STORY: As an IMAGE user, I want to experience a broader variety of chart types, so that I can have a rich IMAGE experience of more chart content on the web. #805, and the separately collected list from @jeffbl have been reviewed.
• Working and useful Highcharts examples are documented in handlers/high-charts/README.md or a more suitable README.md file..
• Working and useful map examples are documented in preprocessors/openstreetmap/README.md or a more suitable README.md file..
• Each example explains what behaviour or feature it exercises.
• Current support or expected results are recorded where known.
• Each example includes a last-verified date.
• The possibility of external links changing or returning 404 errors is clearly documented.
• The documentation is understandable and useful to contributors and partners outside McGill.
• The pull request references this issue.

Out of scope

This issue does not require any programming.