added typescript definitions

added typescript definitions for the plugins:
 - markdown-it-mark
 - markdown-it-ins
 - markdown-it-sub
 - markdown-it-sup

src/external-types/markdown-it-ins/index.d.ts

@@ -0,0 +1,6 @@
+
+declare module 'markdown-it-ins' {
+  import MarkdownIt from 'markdown-it/lib'
+  const markdownItInserted: MarkdownIt.PluginSimple
+  export = markdownItInserted
+}

src/external-types/markdown-it-mark/index.d.ts

@@ -0,0 +1,6 @@
+
+declare module 'markdown-it-mark' {
+  import MarkdownIt from 'markdown-it/lib'
+  const markdownItMark: MarkdownIt.PluginSimple
+  export = markdownItMark
+}

src/external-types/markdown-it-sub/index.d.ts

@@ -0,0 +1,6 @@
+
+declare module 'markdown-it-sub' {
+  import MarkdownIt from 'markdown-it/lib'
+  const markdownItSubscript: MarkdownIt.PluginSimple
+  export = markdownItSubscript
+}

src/external-types/markdown-it-sup/index.d.ts

@@ -0,0 +1,6 @@
+
+declare module 'markdown-it-sup' {
+  import MarkdownIt from 'markdown-it/lib'
+  const markdownItSuperscript: MarkdownIt.PluginSimple
+  export = markdownItSuperscript
+}