clarify horizontal rules

README.md

@@ -28,11 +28,11 @@ A line of normal text with `inline code` and *italics*, **strong font**, and eve
 
 Followed by another line of normal text with `inline code` and *italics*, **strong font**, and even some μ†ℱ ╋ℯ╳╋. Followed by lots of Lorem ipsum dolor sit amet, consectetur adipiscing elit. Duis id sem purus, eu commodo tortor. Donec malesuada ultricies dolor a eleifend. In hac habitasse platea dictumst. Vivamus a faucibus ligula. Nullam molestie tristique arcu, eu elementum metus ultricies sed. Aenean luctus congue lectus, vitae semper erat rhoncus non. Nulla facilisi.
 
-"Line" Separator:
+Thin horizontal rule:
 
 --
 
-"Slanted" Separator:
+Thick horizontal rule:
 
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