ci: document the intended purpose of each workflow

.github/workflows/build-extra.yml

@@ -1,3 +1,5 @@
+# Builds the project with alternative tools.
+
 name: Build-extra
 
 on:

.github/workflows/build.yml

@@ -1,3 +1,6 @@
+# Checks that `make dist` works and builds the project with the default
+# configuration.
+
 name: Build
 
 # Note: Keep this list in sync with DISTFILES in ../../Makefile.

.github/workflows/check-c.yml

@@ -1,3 +1,5 @@
+# Checks for potential issues in the source code.
+
 name: Check-C
 
 on:

.github/workflows/check-profiles.yml

@@ -1,3 +1,5 @@
+# Lints and checks for potential issues in the profiles.
+
 name: Check-Profiles
 
 on:

.github/workflows/check-python.yml

@@ -1,3 +1,5 @@
+# Lints and checks for potential issues in Python files.
+
 name: Check-Python
 
 on:

.github/workflows/codespell.yml

@@ -1,3 +1,5 @@
+# Checks the spelling on all non-third-party files.
+
 name: Codespell
 
 on:

.github/workflows/test.yml

@@ -1,3 +1,5 @@
+# Checks that the tests are passing.
+
 name: Test
 
 on: