doc: add meta.donationPage

This might be a nice way to use our reach to remind users to donate to
FLOSS projects that they use and love.

Signed-off-by: Ethan Carter Edwards <ethan@ethancedwards.com>

doc/redirects.json

@@ -926,6 +926,9 @@
   "var-go-buildTestBinaries": [
     "index.html#var-go-buildTestBinaries"
   ],
+  "var-meta-donationPage": [
+    "index.html#var-meta-donationPage"
+  ],
   "var-meta-identifiers-cpe": [
     "index.html#var-meta-identifiers-cpe"
   ],

doc/stdenv/meta.chapter.md

@@ -61,6 +61,12 @@ Release branch. Used to specify that a package is not going to receive updates t
 
 The package’s homepage. Example: `https://www.gnu.org/software/hello/manual/`
 
+### `donationPage` {#var-meta-donationPage}
+
+The package or project's donation page, if it exists. Example: `https://neovim.io/sponsors/`
+
+Authoritative project URLs are preferred.
+
 ### `downloadPage` {#var-meta-downloadPage}
 
 The page where a link to the current version can be found. Example: `https://ftp.gnu.org/gnu/hello/`