New lint: Puncuate end of sentences.

What it does

This lint suggests to end a sentence with punctuation if there is a newline gap, (two \n\n) or the doc comment ends.

Lint Name

puncuate_end_sentence

Category

pedantic

Advantage

• Documentation is made clearer with punctuation at the end of short sentences and long paragraphs.

Drawbacks

• This lint only works for the end of documentation or where a new line gap is present. Otherwise we would have to embed a grammar engine into clippy.
• This lint is not easily applicable in languages that are not descended from Latin (hence the pedantic category).

Example

/// Returns the meaning of life
fn meaning_of_life() -> u32 {
    42
}

Could be written as:

/// Returns the meaning of life.
fn meaning_of_life() -> u32 {
    42
}

No files, tests, or entry points are named in the issue. Before starting, identify where a new Clippy lint and its tests belong; done means the proposed lint detects sentence endings as described and has coverage for the stated documentation-comment cases.