[Docs] Improve README.md & CONTRIBUTING.md syntax

[PeterDaveHello]

There are four kinds of changes in this PR in a single commit:

• Lists should be surrounded by blank lines
• Use only 1. for ordered list item prefix
• Starting bulleted lists at the beginning of the line
• Fenced code blocks should be surrounded by blank lines

This improvement helps maintain the consistency in the document and the maintainability, readability in the document source.

[PeterDaveHello]

@ljharb anything else I need to do here? Thanks.

[ljharb]

i'm confused why this is an improvement; it seems like it'd render the same in the markdown, but it's much less readable in raw form.

[PeterDaveHello]

It's suggested by the markdownlint tool:
https://github.com/DavidAnson/markdownlint/blob/master/doc/Rules.md#md006---consider-starting-bulleted-lists-at-the-beginning-of-the-line, the lists should start at the beginning of the lines, sounds reasonable?

[ljharb]

No, i don’t agree with that rationale - i don’t care about the editing experience, but the reading experience in raw form is important to me.

[PeterDaveHello]

okay, I'll rollback this one, how about the others? Look good to you?

[ljharb]

i think so; i'll take another look once the diff is updated

[PeterDaveHello]

I have a concern here, some of them, including the table of contents, start from the beginning of the lines, won't this make some inconsistency? and in that case of table of contents, it looks different.

Let me know if I should just "rollback" or the consistency should also be maintained, thanks.

[ljharb]

i guess i'm not sure i see a need for consistency between all lists - lists that are top-level things like a TOC are one thing, and lists that are subpoints of another paragraph are another.

[PeterDaveHello]

Okay, I'll just rollback those changes.

[PeterDaveHello]

@ljharb are we good to go now? Thanks.