Add coq matcher in actions

As per
https://github.com/actions/toolkit/blob/master/docs/commands.md#problem-matchers

h/t actions/setup-go#46 (comment)
for pointing out that this is possible

.github/workflows/coq-macos.yml

@@ -68,6 +68,8 @@ jobs:
     - uses: actions/checkout@v2
     - name: submodules-init
       uses: snickerbockers/submodules-init@v4
+    - name: add Coq matcher
+      run: echo "::add-matcher::.github/coq.json"
     - name: deps
       run: |
         eval $(opam env)

.github/workflows/coq-windows.yml

@@ -78,6 +78,10 @@ jobs:
         C:\cygwin64\bin\bash -l -c 'cd "%cd%"; make printenv'
         C:\cygwin64\bin\bash -l -c 'cd "%cd%"; echo "${PATH}"'
       shell: cmd
+    - name: add Coq matcher
+      run: |
+        C:\cygwin64\bin\bash -l -c 'cd "%cd%"; echo "::add-matcher::.github/coq.json"'
+      shell: cmd
     - name: deps
       run: C:\cygwin64\bin\bash -l -c 'cd "%cd%"; etc/ci/github-actions-make.sh -j%NJOBS% deps'
       shell: cmd

.github/workflows/coq.yml

@@ -46,6 +46,8 @@ jobs:
       with:
         ghc-version: ${{ matrix.ghc }}
         cabal-version: ${{ matrix.cabal }}
+    - name: add Coq matcher
+      run: echo "::add-matcher::.github/coq.json"
     - name: deps
       run: etc/ci/github-actions-make.sh -j2 deps
     - name: all