Improve grammar and .gitignore

[CollieIsCute]

• Add more contents that cursor IDE generates to .gitignore
• According to the Legal writing advice, the "or" word already means "X or Y or both", so we don't need to write "and" again.
• According to merriam-webster dictionary, "Failing that" is a formal idiom, so I correct "Failing this" with that.
• Add some punctuation:
  • Add double quotes to make sentences more clear
  • Add comma before "for example" because of this page
• Use more formal word "nonzero" instead. merriam-webster dictionary lists nonzero as the correct form.
• Add missing be verbs, spaces
• According to collinsdictionary, "management" is an uncountable noun.

Summary by Bito

This pull request enhances documentation by correcting grammatical errors and improving punctuation in 'lkmpg.tex' and 'examples/hello-1.c'. It includes the use of more formal language and aims to improve readability and professionalism.

Unit tests added: False

Estimated effort to review (1-5, lower is better): 2