Use default names for the markdown linter

.github/workflows/check_markdown.yaml

@@ -26,5 +26,3 @@ jobs:
         uses: actions/checkout@v2
 
       - uses: articulate/actions-markdownlint@v1
-        with:
-          config: markdownlint.json

.markdownlintignore

@@ -0,0 +1 @@
+docs/index.md

README.md

@@ -75,7 +75,8 @@ Filename                              |Descriptions
 [mlc_config.json](mlc_config.json)    |Configuration of the link checker, use `markdown-link-check --config mlc_config.json --quiet docs/**/*.md` to do link checking locally
 [.spellcheck.yml](.spellcheck.yml)    |Configuration of the spell checker, use `pyspelling -c .spellcheck.yml` to do spellcheck locally
 [.wordlist.txt](.wordlist.txt)        |Whitelisted words for the spell checker, use `pyspelling -c .spellcheck.yml` to do spellcheck locally
-[markdownlint.json](markdownlint.json)|Configuration of the markdown linter, use `markdownlint --config markdownlint.json **/*.md` to do markdown linting locally
+[.markdownlint.jsonc](.markdownlint.jsonc)|Configuration of the markdown linter, use `markdownlint **/*.md` to do markdown linting locally. The name of this file is a default name.
+[.markdownlintignore](.markdownlintignore)|Files ignored by the markdown linter, use `markdownlint **/*.md` to do markdown linting locally. The name of this file is a default name.
 
 ## Credits