add a little info table for each edition

Author: nikomatsakis

src/rust-2018/index.md

@@ -1,3 +1,9 @@
 # Rust 2018
 
+| Info | |
+| --- | --- |
+| RFC | [#2052](https://rust-lang.github.io/rfcs/2052-epochs.html), which also proposed the Edition system |
+| Release version | [1.31.0](https://blog.rust-lang.org/2018/12/06/Rust-1.31-and-rust-2018.html) |
+
 The edition system was created for the release of Rust 2018. The release of the Rust 2018 edition coincided with a number of other features all coordinated around the theme of *productivity*. The majority of those features were backwards compatible and are now available on all editions; however, some of those changes required the edition mechanism (most notably the [module system changes](path-changes.md)).
+s

src/rust-2021/index.md

@@ -2,6 +2,11 @@
 
 🚧 The 2021 Edition has not yet been released and hence this section is still "under construction".
 
+| Info | |
+| --- | --- |
+| RFC | [#3085](https://github.com/rust-lang/rfcs/pull/3085) |
+| Release version | 1.56.0 (anticipated) |
+
 The Rust 2021 Edition is currently slated for release in Rust 1.56.0.
 Rust 1.56.0 will then be in beta for six weeks,
 after which it is released as stable on October 21st.