Add alchemical planet symbols

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Alchemical symbols for: sun, mercury, earth, moon, jupiter, saturn, uranus and neptune.
closes #1125

Author: me
Descriptions:

• Sun: The alchemical symbol for gold, representing perfection, spirit, and the life force.
• Moon: The alchemical symbol for silver, representing intuition, cycles, and the soul.
• Mercury: The alchemical symbol for quicksilver (mercury), representing fluidity, transformation, and communication between elements.
• Earth: Primarily the astronomical symbol for the planet, later used in alchemy to also represent the metal antimony.
• Jupiter: The alchemical symbol for tin, representing expansion, wisdom, and the process of fermentation.
• Saturn: The alchemical symbol for lead, representing time, limitation, and the necessary stage of purification.
• Uranus: A modern symbol for the planet (discovered in 1781), associated in later esoteric thought with sudden insight, innovation, and breaking convention.
• Neptune: A modern symbol for the planet (discovered in 1846), associated in later esoteric thought with the subconscious, dreams, and the dissolution of boundaries.

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