tidy-up: whitespace, fix CI spacecheck for docs

Also: fixup CI spacecheck to apply to docs again.

Closes #15423

.github/workflows/checkdocs.yml

@@ -147,3 +147,13 @@ jobs:
 
       - name: verify examples
         run: .github/scripts/verify-examples.pl docs/libcurl/curl*.3 docs/libcurl/opts/*.3
+
+  miscchecks:
+    runs-on: ubuntu-24.04
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+        name: checkout
+
+      - name: spacecheck
+        run: .github/scripts/spacecheck.pl

docs/internals/MQTT.md

@@ -14,6 +14,7 @@ Doing a "POST" publishes the post data to the topic and exits.
 
 
 ### Subscribing
+
 Command usage:
 
     curl mqtt://host/topic
@@ -25,6 +26,7 @@ Example subscribe:
 This will send an MQTT SUBSCRIBE packet for the topic `bedroom/temp` and listen in for incoming PUBLISH packets.
 
 ### Publishing
+
 Command usage:
 
     curl -d payload mqtt://host/topic