Add a note to update other files & streamline comments

In some places, the value of a linter configuration property should
match the value of the editor configuration in `.editorconfig`. This is
easily forgotten, so I added a comment to remind us.

Also, I streamlined the introductory comments at the tops of the files
to make them less verbose.

Author: mhucka

.clang-format

@@ -11,11 +11,11 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
-# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-# Basic clang-format config for this project.
+
+# Summary: configure clang-format for this project.
 # See https://clang.llvm.org/docs/ClangFormatStyleOptions.html for more info.
-# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+# Note: if you change line length or indentation here, update .editorconfig too.
 ---
 Language: Cpp
 BasedOnStyle: Google

.hadolint.yaml

@@ -12,11 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-# Hadolint (a Dockerfile linter) used in this project's CI checks.
+# Summary: configure the Dockerfile linter "hadolint" for this project.
 # Info about options can be found at https://github.com/hadolint/hadolint/.
 # Rule/error numbers are described at https://github.com/hadolint/hadolint/wiki
-# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 format: tty
 no-color: false

.jsonlintrc.yaml

@@ -12,14 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-# Project configuration for jsonlint (https://github.com/prantlf/jsonlint).
-# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# Summary: configure https://github.com/prantlf/jsonlint for this project.
 
 comments: false
 compact: true
 continue: true
 endOfLine: lf
+# Note: if you change indentation or line length, update .editorconfig too.
 indent: 2
 log-files: false
 no-duplicate-keys: true

.markdownlintrc

@@ -13,8 +13,7 @@
   // See the License for the specific language governing permissions and
   // limitations under the License.
 
-  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-  // Markdownlint linter configuration for this project.
+  // Summary: configure markdownlint for this project.
   //
   // Note: there are multiple programs programs named "markdownlint". We use
   // https://github.com/igorshubovych/markdownlint-cli/, which is the one you
@@ -28,7 +27,6 @@
   // https://github.com/DavidAnson/markdownlint/blob/main/doc/Rules.md
   // (Beware that the above looks similar but is NOT the same as the page
   // https://github.com/markdownlint/markdownlint/blob/main/docs/RULES.md.)
-  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
   "$schema": "https://raw.githubusercontent.com/DavidAnson/markdownlint/main/schema/markdownlint-config-schema.json",
 

.yamlfmt.yaml

@@ -12,17 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-# yamlfmt configuration for this project.
+# Summary: configure yamlfmt for this project.
 # See https://github.com/google/yamlfmt for info about options.
-# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 # Read .gitignore for paths to exclude.
 gitignore_excludes: true
 
 formatter:
   type: basic
   eof_newline: true
+# Note: if you change the line length here, update .editorconfig too.
   max_line_length: 80
   retain_line_breaks: true
   trim_trailing_whitespace: true

.yamllint.yaml

@@ -12,13 +12,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-# Yamllint configuration to match project settings like line length.
+# Summary: configure yamllint for this project.
 # See https://yamllint.readthedocs.io/ for info about configuration options.
-# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 rules:
   line-length:
+    # Note: if you change the line length here, update .editorconfig too.
     max: 80
     # When the last item on a line can't be broken (e.g., a URL as a value),
     # it's rarely useful to flag it. The next 2 settings save developer time by