Add warning for downloading large amounts of data (more than 100MB(?))

[rwood-97]

Summary

This PR:

• adds code to work out how much data you will likely download when running any of the 'download' functions
• adds a warning if its over 100MB and raises an error
• adds a 'force' argument so that you can bypass this error

Fixes #444

Checklist before assigning a reviewer (update as needed)

• [x] Self-review code
• [x] Ensure submission passes current tests
• [x] Add tests
• [x] Update relevant docs

Reviewer checklist

Please add anything you want reviewers to specifically focus/comment on.

• [ ] Everything looks ok?

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 72.94118% with 23 lines in your changes missing coverage. Please review.

Project coverage is 62.77%. Comparing base (f8b7c0f) to head (9fa8caf). Report is 3 commits behind head on main.

Files	Patch %	Lines
mapreader/download/downloader.py	13.04%	20 Missing :warning:
mapreader/download/sheet_downloader.py	85.71%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #464 +/- ## ========================================== - Coverage 62.83% 62.77% -0.07% ========================================== Files 41 41 Lines 6757 6807 +50 ========================================== + Hits 4246 4273 +27 - Misses 2511 2534 +23 ``` | [Flag](https://app.codecov.io/gh/Living-with-machines/MapReader/pull/464/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Living-with-machines) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/Living-with-machines/MapReader/pull/464/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Living-with-machines) | `62.77% <72.94%> (-0.07%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Living-with-machines#carryforward-flags-in-the-pull-request-comment) to find out more.

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