Add elevation mapping (#243)

Introduces robot-centric elevation mapping using the Grid Map library. Includes:
- New article: wiki/sensing/elevation-mapping.md
- Standardized and alphabetically sorted Sensing navigation in _data/navigation.yml and wiki/sensing/index.md.
- Added missing Sensing articles to the sidebar and index.
- Corrected various link inconsistencies within the Sensing section.

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Co-authored-by: Kshitij Kabeer <kshitijkabeer@gmail.com>
Co-authored-by: harshad_zade <zade@jpl.nasa.gov>

Author: 3 people