Apply some light edits to the markdown chapter

Author: ehuss

reference-dev-guide/src/formatting/markdown.md

@@ -5,27 +5,27 @@ There are automated checks for some of these rules. Run [`cargo xtask style-chec
 ## Formatting style
 
 - Use [ATX-style headings][atx] (not Setext) with [sentence case].
-- Do not use tabs, only spaces.
+- Do not use tabs; use only spaces.
 - Files must end with a newline.
-- Lines must not end with spaces. Double spaces have semantic meaning, but can be invisible. Use a trailing backslash if you need a hard line break.
+- Lines must not end with spaces. Double spaces have semantic meaning but can be invisible. Use a trailing backslash if you need a hard line break.
 - If possible, avoid double blank lines.
 - Do not wrap long lines. This helps with reviewing diffs of the source.
-- Use [smart punctuation] instead of Unicode characters. For example, use `---` for em-dash instead of the Unicode character. Characters like em-dash can be difficult to see in a fixed-width editor, and some editors may not have easy methods to enter such characters.
+- Use [smart punctuation] instead of Unicode characters. For example, use `---` for an em-dash instead of the Unicode character. Characters like the em-dash can be difficult to see in a fixed-width editor, and some editors may not have easy methods to enter such characters.
 - See the [admonitions chapter] for formatting callouts such as notes, edition differences, and warnings.
 
 ## Code blocks
 
-- Do not use indented code blocks; use 3+ backticks code blocks instead.
+- Do not use indented code blocks; use fenced code blocks with 3+ backticks instead.
 - Code blocks should have an explicit language tag.
 
 ## Links
 
 See the [links chapter] for more information about linking.
 
-- Links to other chapters should be relative with the `.md` extension.
+- Links to other chapters should be relative and use the `.md` extension.
 - Links to other rust-lang books that are published with the Reference should also be relative so that the linkchecker can validate them. See [outside book links].
-- Links to the standard library should use rustdoc-style links described in [standard library links].
-- The use of reference links is preferred, with shortcuts if appropriate. Place the sorted link reference definitions at the bottom of the file or at the bottom of a section if there are an unusually large number of links that are specific to the section.
+- Links to the standard library should use rustdoc-style links as described in [standard library links].
+- The use of reference links is preferred, with shortcuts if appropriate. Place sorted link reference definitions at the bottom of the file, or at the bottom of a section if there is an unusually large number of links specific to that section.
 
     ```markdown
     Example of shortcut link: [enumerations]