New Lithium Carbonate Structure Missing from Examples tab

[PNOGillespie]

Describe the bug
A structure for lithium carbonate (Li₂CO₃) was added to the example structures in the PR for XAS documentation (#614) and is used in the documentation, however the entry in src/aiidalab-qe/app/structure/__init__.py is missing:

Examples = [
    ("Silicon (diamond)", file_path / "examples" / "Si.xyz"),
    ("Silicon oxide", file_path / "examples" / "SiO2.xyz"),
    ("Diamond", file_path / "examples" / "diamond.cif"),
    ("Gallium arsenide", file_path / "examples" / "GaAs.xyz"),
    ("Gold (fcc)", file_path / "examples" / "Au.cif"),
    ("Cobalt (hcp)", file_path / "examples" / "Co.cif"),
]

As a result, the structure isn't loadable from the From examples tab.
Version (if known)

• App version: [e.g. v24.04.0a2]

[PNOGillespie]

@superstar54, I'll add a PR for this shortly