Add new QUERY_EXTERNAL_BLOCKED_EDE15 query status

Signed-off-by: DL6ER <dl6er@dl6er.de>

docs/database/ftl.md

@@ -132,6 +132,7 @@ ID | Status | | Details
 15 | Blocked | ❌ | Blocked (database is busy)<br> How these queries are handled can be [configured](../ftldns/configfile.md#reply_when_busy)
 16 | Blocked | ❌ | Blocked (special domain)<br>*E.g. Mozilla's canary domain and Apple's Private Relay domains* <br> Handling can be [configured](../ftldns/configfile.md)
 17 | Allowed | ✅⌛ | Replied from *stale* cache
+18 | Blocked | ❌ | By upstream server (EDE 15)
 
 ### Supported reply types
 

docs/ftldns/debugging.md

@@ -31,7 +31,7 @@ Once you are used to it, you can skip most of the steps. Debugging *FTL*DNS is q
 
 ## Prerequirements (only required once)
 
-1. Install `screen` and `gdb` using `sudo apt-get install screen gdb` (you may need to use another package manager, e.g., `yum`, `dnf` or `apk add`, depending on your distribution)
+1. Install `screen` and `gdb` using `sudo apt install screen gdb` (you may need to use another package manager, e.g., `yum`, `dnf` or `apk add`, depending on your distribution)
 2. Start a screen session (it will allow you to come back even if the SSH connection died)
     * If you don't know about `screen`, then read about it (you *will* love it!)
 3. Start a screen session using `screen`