r: add esr.md, fflastpass.md & firefox.md

* All downloads of Firefox Extended Support Release
* LastPass for Firefox (some redirects go to this file)
* All downloads of Firefox
    * At time of committing this is very difficult to find and I found
      here by editing URL of Firefox beta equivalent.

r/esr.md

@@ -0,0 +1,5 @@
+---
+redirect_to: https://www.mozilla.org/en-US/firefox/organizations/all/
+permalink: /r/esr.html
+sitemap: false
+---

r/fflastpass.md

@@ -0,0 +1,8 @@
+---
+redirect_to: https://lastpass.eu/lastpassffx/xpi.php
+permalink: /r/fflastpass.html
+redirect_from:
+  - /r/firefoxlastpass.html
+  - /r/lastpassfirefox.html
+sitemap: false
+---

r/firefox.md

@@ -0,0 +1,5 @@
+---
+redirect_to: https://www.mozilla.org/en-US/firefox/all/
+permalink: /r/firefox.html
+sitemap: false
+---