ci: migrate link checks to flint

Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

Author: zeitlinger

.github/config/flint.toml

@@ -0,0 +1,3 @@
+[checks.lychee]
+config = "lychee.toml"
+check_all_local = true

mise.toml

@@ -1,7 +1,12 @@
 [tools]
+# Linters
+"github:grafana/flint" = "0.20.3"
 lychee = "0.23.0"
 markdownlint-cli2 = "0.22.0"
 
+[env]
+FLINT_CONFIG_DIR = ".github/config"
+
 [settings]
 # Only install tools explicitly defined in the [tools] section above
 idiomatic_version_file_enable_tools = []
@@ -12,7 +17,6 @@ windows_executable_extensions = ["sh"]
 windows_default_file_shell_args = "bash"
 use_file_shell_for_executable_tasks = true
 
-# Pick the tasks you need from flint (https://github.com/grafana/flint)
 [tasks."lint:links"]
 description = "Check for broken links in changed files + all local links"
-file = "https://raw.githubusercontent.com/grafana/flint/eded4cd370c729289a6de327a1a26831e10a39b9/tasks/lint/links.sh" # v0.20.2
+run = "flint run lychee"