[Documentation] (Issue 728) Fix/improve Lasagna introduction.md

[adamazing]

What this fixes:

• Issues/improvements raised in issue Documentation: introduction.md improvements / fixes for Lasagna #728:
  • Two sentences that seem to say the same thing (drawing the distinction between explicit type annotation and implicit typing by the compiled)
  • Spelling errors
  • Possible misuse of 'parse' for 'pass'?
  • Transposition of words (s/are functions/functions are/)

Related issue: #728

[meatball133]

I am a bit unsure of using an example for writing comments. Since there are multiple occasions in other examples examples are used and I don't know if a specific example for comment is hence needed.

Changes should also be applied to the following files:

• concept:basic:about.md
• concept:basic:introduction.md