Grammatical adjustments to Nix Pill 19

[camelpunch]

• tense corrections e.g. "did dive" -> "dived"
• pluralisation corrections
• "is not a special derivation to Nix" -> "is not treated as a special derivation by Nix"
• add question marks to headings phrased as questions, or transform them into statements
• sentence separation and removal of semicolons
• adverb corrections e.g. "enough contained" -> "sufficiently contained"
• links to sources in GitHub where they felt frustratingly missing