fix: more error handling for files that will never contain docblocks (#…

…321)

Follow on from this PR: #196
which added support for ignoring `multiline-extract-comments` from markdown
files. We only accounted for `.md` extensions and not `.markdown`, which is
also valid.

This will fix an error upstream in the readme-micro action which uses
swagger-inline to try and extract openapi operations from code.

__tests__/__fixtures__/project-openapi/README.markdown

@@ -0,0 +1,3 @@
+This is a test README.
+
+It should not be picked up by `swagger-inline` and throw errors because it doesn't have any docblocks.

src/index.js

@@ -134,7 +134,7 @@ function swaggerInline(globPatterns, providedOptions) {
                   });
                 } catch (err) {
                   // If the file that we failed to parse is a text file, let's just ignore it.
-                  if (['.json', '.md', '.txt'].includes(path.extname(fileInfo.fileName))) {
+                  if (['.json', '.md', '.markdown', '.txt'].includes(path.extname(fileInfo.fileName))) {
                     return Promise.resolve();
                   } else if (/Cannot find language definition/.test(err.message)) {
                     return Promise.resolve();