Total rubbish. Ignore all that , Jocat, you aren't deficient in magnesium, and you certainly can't absorb it by sitting in a bath of Epsom Salt, that's what skin is for. Magnesium deficiency can cause a host of severe systemic symptoms - muscle weakness, lethargy, muscle spasms and cardiac failure. I know, I've had it, caused by years of taking omeprazole. You can also get it by being alcoholic. What it doesn't cause is plantar fasciitis, and if it doesn't cause it, it can't cure it.
And just because it's on Google doesn't make it true, there are thousands of cures for diabetes on Google. And you could have saved your money Chili. if you take care, it will go away in a month anyway. I almost needn't bother adding that zinc deficiency doesn't cause plantar fasciitis either.
Having said that, I really can't be bothered refuting the idea that you can eat particular foods to cure fasciitis, it's too daft for words.
Stick to what the doctor told you, and Lillian's advice about footwear.