docs: add reason lines to the rollup-plugin-terser, tsup and cpx docs

docs/modules/cpx.md

@@ -4,6 +4,8 @@ description: Modern alternatives to the cpx package for copying file globs with
 
 # Replacements for `cpx`
 
+`cpx` hasn't had a release since 2016 and has bugs and performance issues that are fixed by its replacement
+
 ## `cpx2`
 
 [`cpx`](https://github.com/mysticatea/cpx) is unmaintained. [`cpx2`](https://github.com/bcomnes/cpx2) is an actively maintained fork that keeps the same CLI bin name (`cpx`), so it works as a drop-in replacement for CLI usage. For the Node API, switch your import to `cpx2`.

docs/modules/rollup-plugin-terser.md

@@ -4,6 +4,8 @@ description: Modern alternatives to the rollup-plugin-terser package for minifyi
 
 # Replacements for `rollup-plugin-terser`
 
+`rollup-plugin-terser` is deprecated and archived, and the Rollup team now maintains it as `@rollup/plugin-terser`.
+
 ## `@rollup/plugin-terser`
 
 [`rollup-plugin-terser`](https://github.com/TrySound/rollup-plugin-terser) is deprecated and no longer maintained. [`@rollup/plugin-terser`](https://github.com/rollup/plugins/tree/master/packages/terser) is its official successor, maintained by the Rollup team. The options are unchanged, but the plugin is now a default export rather than a named one.

docs/modules/tsup.md

@@ -4,6 +4,8 @@ description: Modern alternative to tsup for bundling TypeScript libraries
 
 # Replacements for `tsup`
 
+The `tsup` README says the project is no longer actively maintained and recommends `tsdown` instead.
+
 ## `tsdown`
 
 [tsdown](https://github.com/rolldown/tsdown) is the successor recommended by [tsup's own README](https://github.com/egoist/tsup). The project is effectively in maintenance mode. tsdown is built on Rolldown and is typically faster for library builds, with a largely drop-in config surface.