Add 'lowdown' to build dependencies so GitHub actions actually runs it

Building the man page is optional and happens automatically if command
'lowdown' is present on the system. Add it to the Snap definition and to
all GitHub CI files so man page conversion will be tested and fully used.

Unfortunately 'lowdown' cannot be added to the musl jobs the program is
available only starting from Alpine v3.15, while the musl Docker images
run Alpine v3.14 (and haven't been updated in 2+ years).

.github/workflows/cmake-freebsd.yml

@@ -33,8 +33,7 @@ jobs:
         with:
           release: '14.0'
           usesh: true
-          prepare: pkg install -y cmake ninja
+          prepare: pkg install -y cmake ninja lowdown
           run: |
             CXX=clang++ cmake -B build -G Ninja -DBTOP_STATIC=ON
             cmake --build build --verbose
-

.github/workflows/cmake-linux.yml

@@ -30,11 +30,10 @@ jobs:
       - uses: actions/checkout@v4
 
       - name: Install build tools
-        run: apk add --no-cache --update clang cmake lld ninja
+        run: apk add --no-cache --update clang cmake lld ninja lowdown
 
       - name: Configure
         run: CXX=clang++ LDFLAGS=-fuse-ld=lld cmake -B build -G Ninja -DBTOP_STATIC=ON
 
       - name: Compile
         run: cmake --build build --verbose
-

.github/workflows/cmake-macos.yml

@@ -32,7 +32,7 @@ jobs:
         run: |
           export HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK=1
           brew update --quiet
-          brew install --force --overwrite cmake llvm@17 ninja
+          brew install --force --overwrite cmake llvm@17 ninja lowdown
 
       - name: Configure
         run: |
@@ -44,4 +44,3 @@ jobs:
 
       - name: Compile
         run: cmake --build build --verbose
-

.github/workflows/continuous-build-freebsd.yml

@@ -45,7 +45,7 @@ jobs:
           release: '14.0'
           usesh: true
           prepare: |
-            pkg install -y gmake gcc coreutils git
+            pkg install -y gmake gcc coreutils git lowdown
             git config --global --add safe.directory /home/runner/work/btop/btop
           run: |
             CXX=${{ matrix.compiler }} gmake STATIC=true STRIP=true
@@ -59,4 +59,3 @@ jobs:
           name: btop-x86_64-freebsd-14
           path: 'bin/*'
           if-no-files-found: error
-

.github/workflows/continuous-build-openbsd.yml

@@ -42,7 +42,7 @@ jobs:
           release: '7.4'
           usesh: true
           prepare: |
-            pkg_add gmake gcc%11 g++%11 coreutils git
+            pkg_add gmake gcc%11 g++%11 coreutils git lowdown
             git config --global --add safe.directory /home/runner/work/btop/btop
           run: |
             gmake CXX=eg++ STATIC=true STRIP=true
@@ -55,4 +55,3 @@ jobs:
           name: btop-x86_64-openbsd-7.4
           path: 'bin/*'
           if-no-files-found: error
-

snap/snapcraft.yaml

@@ -56,7 +56,8 @@ parts:
       - build-essential
       - gcc-11
       - g++-11
-
+      - lowdown
+
     override-pull: |
       snapcraftctl pull
       snapcraftctl set-version "$(git describe --tags | sed 's/^v//' | cut -d "-" -f1)"