Add lang + ref tags to frontmatter

Those are fields used by the language switcher to correlate pages across
different languages, even if they have different names/paths/titles.
They are generated with the prepare_for_translation.py script.

developer/releases/1_0/release-notes.md

@@ -1,8 +1,10 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/1.0/release-notes/
 redirect_from:
 - /en/doc/releases/1.0/release-notes/
+ref: 18
 title: Qubes R1.0 Release Notes
 ---
 

developer/releases/2_0/release-notes.md

@@ -1,8 +1,10 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/2.0/release-notes/
 redirect_from:
 - /en/doc/releases/2.0/release-notes/
+ref: 25
 title: Qubes R2.0 Release Notes
 ---
 

developer/releases/3_0/release-notes.md

@@ -1,8 +1,10 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/3.0/release-notes/
 redirect_from:
 - /en/doc/releases/3.0/release-notes/
+ref: 19
 title: Qubes R3.0 Release Notes
 ---
 

developer/releases/3_0/schedule.md

@@ -1,8 +1,10 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/3.0/schedule/
 redirect_from:
 - /en/doc/releases/3.0/schedule/
+ref: 20
 title: Qubes R3.0 Release Schedule
 ---
 

developer/releases/3_1/release-notes.md

@@ -1,6 +1,8 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/3.1/release-notes/
+ref: 16
 title: Qubes R3.1 release notes
 ---
 

developer/releases/3_1/schedule.md

@@ -1,8 +1,10 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/3.1/schedule/
 redirect_from:
 - /en/doc/releases/3.1/schedule/
+ref: 17
 title: Qubes R3.1 Release Schedule
 ---
 

developer/releases/3_2/release-notes.md

@@ -1,6 +1,8 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/3.2/release-notes/
+ref: 21
 title: Qubes R3.2 release notes
 ---
 

developer/releases/3_2/schedule.md

@@ -1,8 +1,10 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/3.2/schedule/
 redirect_from:
 - /en/doc/releases/3.2/schedule/
+ref: 22
 title: Qubes R3.2 Release Schedule
 ---
 

developer/releases/4_0/release-notes.md

@@ -1,6 +1,8 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/4.0/release-notes/
+ref: 23
 title: Qubes R4.0 release notes
 ---
 

developer/releases/4_0/schedule.md

@@ -1,8 +1,10 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/4.0/schedule/
 redirect_from:
 - /en/doc/releases/4.0/schedule/
+ref: 24
 title: Qubes R4.0 Release Schedule
 ---
 

developer/releases/notes.md

@@ -1,6 +1,8 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/notes/
+ref: 13
 title: Release Notes
 ---
 

developer/releases/schedules.md

@@ -1,6 +1,8 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/schedules/
+ref: 15
 title: Release Schedules
 ---
 

developer/releases/todo.md

@@ -1,8 +1,10 @@
 ---
+lang: en
 layout: doc
 permalink: /doc/releases/todo/
 redirect_from:
 - /en/doc/releases/todo/
+ref: 14
 title: Release Checklist
 ---