Add the check-spelling.sh script (#23)

This script checks spelling in `gravitational/docs`. Add this script to
`gravitational/docs-website` to ensure parity in our docs CI workflow.

scripts/check-spelling.sh

@@ -0,0 +1,44 @@
+# $1 is the content directory in which to check spelling. A content directory is
+# a git submodule pointing to a branch of the gravitational/teleport repository.
+
+if [ $# -eq 0 ]; then
+
+    cat<<EOF
+
+You must provide an argument to the spellcheck script. The argument must be the
+path to a content directory, which is either:
+
+- A subdirectory of "content" within a gravitational/docs clone
+- The root of a gravitational/teleport clone
+
+EOF
+exit 1;
+fi
+
+if [ ! -e $1/docs/cspell.json ]; then
+
+    cat<<EOF
+
+We could not find $1/docs/cspell.json. Make sure you run the spellcheck script
+on either:
+
+- A subdirectory of "content" within a gravitational/docs clone
+- The root of a gravitational/teleport clone
+
+EOF
+exit 1;
+fi
+
+npx cspell lint --no-progress --config $1/docs/cspell.json "$1/docs/pages/**/*.mdx" "$1/CHANGELOG.md";
+RES=$?;
+if [ $RES -ne 0 ]; then
+  cat<<EOF
+
+There are spelling issues in one or more pages within $1/docs/pages (see the
+logs above). Either fix the misspellings or, if these are not actually issues,
+edit the list of ignored words in $1/docs/cspell.json.
+
+EOF
+exit $RES;
+fi
+