Add link to Tails website

[apyrgio]

Point users to the installation instructions of Dangerzone in the Tails website. These instructions were recently added to Tails, and we have worked with the Tails developers to make this integration happen.

See also:

• https://tails.net/news/dangerzone/index.en.html
• https://gitlab.tails.boum.org/tails/tails/-/issues/20355

[apyrgio]

Merged with the suggested fixes:

diff --git a/INSTALL.md b/INSTALL.md                                                                                   
index 76a3b5e..3aeaf06 100644                                                                                          
--- a/INSTALL.md                                                                                                       
+++ b/INSTALL.md                                                                                                       
@@ -257,9 +257,9 @@ pass it a file to sanitize.      
 ## Tails                                                                                                              

 Dangerzone is not yet available by default in Tails, but we have collaborated       
-with the Tails team to offer some manual                                                                              
+with the Tails team to offer manual                                                                                   
 [installation instructions](https://tails.net/doc/persistent_storage/additional_software/dangerzone/index.en.html)    
-to Tails users.                                                                                                       
+for Tails users.                                                                                                      

 ## Build from source  

Thanks for the review Kunal!