add markdown linting to makefile and github actions (reference: #464)

.github/workflows/build-check.yaml

@@ -111,3 +111,15 @@ jobs:
 
     - name: run markdown-link-check
       run: make markdown-link-check
+
+  markdownlint:
+    runs-on: ubuntu-latest
+    steps:
+    - name: check out code
+      uses: actions/checkout@v2
+
+    - name: install dependencies
+      run: npm install
+
+    - name: run markdownlint
+      run: make markdownlint

.markdownlint.yaml

@@ -0,0 +1,14 @@
+# See https://github.com/DavidAnson/markdownlint/blob/main/doc/Rules.md
+# and https://github.com/DavidAnson/markdownlint/blob/main/README.md
+
+# Default state for all rules
+default: true
+
+ul-style: false
+line-length: false
+no-duplicate-header:
+  siblings_only: true
+ol-prefix:
+  style: ordered
+no-inline-html: false
+fenced-code-language: false

CHANGELOG.md

@@ -58,7 +58,7 @@ Full list of differences found in [this compare](https://github.com/open-telemet
 * Add `csharp_namespace` option to protos.
   ([#399](https://github.com/open-telemetry/opentelemetry-proto/pull/399))
 * Fix some out-of-date urls which link to [specification](https://github.com/open-telemetry/opentelemetry-specification). ([#402](https://github.com/open-telemetry/opentelemetry-proto/pull/402))
-* :stop_sign: [BREAKING] Delete deprecated InstrumentationLibrary, 
+* :stop_sign: [BREAKING] Delete deprecated InstrumentationLibrary,
   InstrumentationLibraryLogs, InstrumentationLibrarySpans and
   InstrumentationLibraryMetrics messages. Delete deprecated
   instrumentation_library_logs, instrumentation_library_spans and
@@ -137,7 +137,7 @@ Full list of differences found in [this compare](https://github.com/open-telemet
 
 * Remove unused deprecated message StringKeyValue (#358)
 * Remove experimental metrics config service (#359)
- 
+
 ## 0.12.0 - 2022-01-19
 
 Full list of differences found in [this compare](https://github.com/open-telemetry/opentelemetry-proto/compare/v0.11.0...v0.12.0).
@@ -288,9 +288,9 @@ Full list of differences found in [this compare.](https://github.com/open-teleme
 ### Changed
 
 * :stop_sign: [BREAKING] Metrics - protocol was refactored, and lots of breaking changes.
-** Removed MetricDescriptor and embedded into Metric and the new data types.
-** Add new data types Gauge/Sum/Histogram.
-** Make use of the "AggregationTemporality" into the data types that allow that support.
+  * Removed MetricDescriptor and embedded into Metric and the new data types.
+  * Add new data types Gauge/Sum/Histogram.
+  * Make use of the "AggregationTemporality" into the data types that allow that support.
 * Rename enum values to follow the proto3 style guide.
 
 ### Added

Makefile

@@ -14,7 +14,7 @@ $(1)
 endef
 
 .PHONY: all
-all: gen-all markdown-link-check
+all: gen-all markdown-link-check markdownlint
 
 # Generate all implementations
 .PHONY: gen-all
@@ -165,3 +165,12 @@ markdown-link-check:
 		npx --no -- markdown-link-check --quiet --config .markdown_link_check_config.json $$f \
 			|| exit 1; \
 	done
+
+.PHONY: markdownlint
+markdownlint:
+	@if ! npm ls markdownlint; then npm install; fi
+	@for f in $(ALL_DOCS); do \
+		echo $$f; \
+		npx --no -p markdownlint-cli markdownlint -c .markdownlint.yaml $$f \
+			|| exit 1; \
+	done