Improve grammar, typos in introduction.mdx

[rmschindler]

Add Oxford comma; correct misspelled abbreviation ‘Wasm’; change ‘Installing’ in heading to ‘Install’, to be consistent with other headings; correct misspelled past tense of the verb ‘set up’, correct grammar in paragraph under ‘Next steps’.

Description

Fixes #0000

Checklist

• [ ] I have reviewed my own code
• [ ] I have added tests

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