Add link for interactive xlsform editing during project creation

[spwoodcock]

What type of PR is this? (check all applicable)

• 🍕 Feature
• 🐛 Bug Fix
• 📝 Documentation
• 🧑‍💻 Refactor
• ✅ Test
• 🤖 Build or CI
• ❓ Other (please specify)

Describe this PR

Do not merge this code, as I first need to be granted a license for using the Excel/spreadsheet web component (it is normally commercial, but they can provide an NGO license, tbc).

• Updated logic for XLSForm loading at backend startup. Removes old forms that no longer exist.
• Currently only the buildings form is available, after the Entity update.
• Added a comment that users should extend an existing XLSForm if they want to provide a custom form.
• Added a link during project creation to download the template form.
• Also added a link to an interactive XLSX editor, with the form preloaded (essentially Excel in the browser!).

Screenshots

Alternative Approaches Considered

• I did a lot of research and dug into the XForm editing functionality of KoboToolbox.
• It's quite a convoluted mess, using CoffeeScript - I struggled to even load the code.
• At some point we could get inspiration from this and have a fully embedded XForm editor in FMTM.

This is the Kobo implementation - a little outdated, but still pretty nice:

Review Guide

• Click the buttons, edit the XLSForm, save the form.
• The XLSForm editor is available at https://xlsforms.fmtm.dev

Checklist before requesting a review

• 📖 Read the FMTM Contributing Guide: https://github.com/hotosm/fmtm/blob/main/CONTRIBUTING.md
• 📖 Read the HOT Code of Conduct: https://docs.hotosm.org/code-of-conduct
• 👷‍♀️ Create small PRs. In most cases, this will be possible.
• ✅ Provide tests for your changes.
• 📝 Use descriptive commit messages.
• 📗 Update any related documentation and include any relevant screenshots.

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