New DEA Mangroves notebook for inclusion with DEA products notebooks …

PR to merge develop into stable to publish the new mangroves notebook

…(#1131)

New DEA Mangroves notebook for inclusion with DEA products notebooks
cleared all cells and re-ran to prepare notebook for publishing
added DEA_Mangroves to the test cube for all dates in tile x49/y24 to match the default analysis area in the mangroves notebook
Minor edits to describe not_observed class in relation to the time-series analysis
Updated index link
Incorporates PR reviews

Thanks for the reviews @robbibt

Include a brief description of the changes being proposed, and why they are necessary.

[ ] Notebook created using the DEA-notebooks template
[ ] Remove any unused Python packages from Load packages
[ ] Remove any unused/empty code cells
[ ] Remove any guidance cells (e.g. General advice)
[ ] Ensure that all code cells follow the PEP8 standard for code. The jupyterlab_code_formatter tool can be used to format code cells to a consistent style: select each code cell, then click Edit and then one of the Apply X Formatter options (YAPF or Black are recommended).
[ ] Include relevant tags in the final notebook cell (refer to the DEA Tags Index, and re-use tags if possible)
[ ] Clear all outputs, run notebook from start to finish, and save the notebook in the state where all cells have been sequentially evaluated
[ ] Test notebook on both the NCI and DEA Sandbox (flag if not working as part of PR and ask for help to solve if needed)
[ ] If applicable, update the Notebook currently compatible with the NCI|DEA Sandbox environment only line below the notebook title to reflect the environments the notebook is compatible with

GeoscienceAustralia / dea-notebooks