CI: refactor spelling check

let us switch to codespell github actions instead of invocation from cmdline.
also, "ifset,thrid,strack,ba,chck,hel,unx,mor" added to whitelist, those are
variable names and special terms widely used in HAProxy

.github/workflows/codespell.yml

@@ -12,12 +12,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-    - name: Install codespell
-      run: sudo pip install codespell
-    - name: Run codespell
-      run: |
-        codespell \
-          -c \
-          -q 2 \
-          --ignore-words-list ist,ists,hist,wan,ca,cas,que,ans,te,nd,referer,ot,uint,iif,fo,keep-alives,dosen \
-          --skip="CHANGELOG,Makefile,*.fig,*.pem"
+    - uses: codespell-project/codespell-problem-matcher@v1
+    - uses: codespell-project/actions-codespell@master
+      with:
+        skip: CHANGELOG,Makefile,*.fig,*.pem
+        ignore_words_list: ist,ists,hist,wan,ca,cas,que,ans,te,nd,referer,ot,uint,iif,fo,keep-alives,dosen,ifset,thrid,strack,ba,chck,hel,unx,mor