Fix spacing in name computation

.changeset/afraid-beers-share.md

@@ -0,0 +1,9 @@
+---
+"@siteimprove/alfa-aria": patch
+---
+
+**Fixed:** Alfa now correctly handle spaces in accessible names. 
+
+* `<br>` elements add a space to the name.
+* Text nodes with leading or trailing spaces (including space only nodes) keep the space when concatenated.
+* Names of descendants with an `aria-label` are spaced, following browsers' behavior.

.changeset/thick-hornets-accept.md

@@ -0,0 +1,5 @@
+---
+"@siteimprove/alfa-aria": minor
+---
+
+**Breaking:** `Name.Source` and `Name.State` are now exported from the top-level of the package.

.changeset/wicked-trains-scream.md

@@ -0,0 +1,5 @@
+---
+"@siteimprove/alfa-dom": patch
+---
+
+**Fixed:** `Node.toString()` now stops dropping text nodes with only spaces.