fix: no markdown check for testthat snaps (#12)

- Tries to make markdownlint not check snapshots used in `test that::expect_snapshot()`
- Adds a `.lycheeignore` file. Right now just with a dead URL generated by favicon

Author: akselthomsen

.github/linters/. lycheeignore

@@ -0,0 +1 @@
+http://svgjs.dev/svgjs

.github/linters/.mega-linter.yml

@@ -7,3 +7,4 @@ ADDITIONAL_EXCLUDED_DIRECTORIES:
   - dev
 SPELL_LYCHEE_FILE_EXTENSIONS: "*"
 SPELL_CSPELL_ANALYZE_FILE_NAMES: false
+MARKDOWN_MARKDOWNLINT_FILTER_REGEX_INCLUDE: "tests/testthat/_snaps"

.github/workflows/megalinter.yaml

@@ -31,8 +31,9 @@ jobs:
       - name: Copy linting config from r.workflows/main
         shell: bash
         run: | 
-          curl --output .mega-linter.yml  https://raw.githubusercontent.com/NovoNordisk-OpenSource/r.workflows/main/.github/linters/.mega-linter.yml
-          curl --output .lintr  https://raw.githubusercontent.com/NovoNordisk-OpenSource/r.workflows/main/.github/linters/.lintr
+          curl --output .mega-linter.yml https://raw.githubusercontent.com/NovoNordisk-OpenSource/r.workflows/main/.github/linters/.mega-linter.yml
+          curl --output .lintr https://raw.githubusercontent.com/NovoNordisk-OpenSource/r.workflows/main/.github/linters/.lintr
+          curl --output .lycheeignore https://raw.githubusercontent.com/NovoNordisk-OpenSource/r.workflows/main/.github/linters/.lycheeignore
           if [ -e "inst/WORDLIST" ]; then
             curl --output .cspell.json https://raw.githubusercontent.com/NovoNordisk-OpenSource/r.workflows/main/.github/linters/.cspell-wordlist.json
           else