No one created Sanskrit as it is Vedavani (language of Veda) and the language of nature. There is also no origin to Sanskrit as it is eternal. But how Sanskrit came to be known to humans is narrated to child Aitareya by his father and is found in the Aitareya Upanishad.
Shiva in his Nataraja form performed a great dance in the center of the universe. Shiva was the dancer, the dance and the audience. With bells ringing and flames encircling him, he danced, his braided hair whirling as he spun round and round. In his left hand he held the flame of destruction and in his right hand he held the drum of creation – damaru. He swung the drum from side to side, measuring the rhythm of the dance.
From the pulse of that small drum came forth the Sanskrit alphabet and from those sounds came forth all forms. The alphabet was heard by the sage Panini. He recorded the cognition in fourteen short verses, called the Shiva Sutras. Sage Panini placed these sutras in the beginning of his Sanskrit Grammar.
Source - Eternal Stories from the Upanishads By Thomas Egenes, Kumuda Reddy