fix(docs): Fix typos in several .md files (#2627)

CONTRIBUTING.md

@@ -28,7 +28,7 @@ What kind of plugins should/could be created? Some inspiration from the 120+ plu
 
 ## Suggesting a plugin
 
-If you start developing a plugin that you aim to release as open source, we suggest that you create a new [new Issue](https://github.com/spotify/backstage/issues/new?labels=plugin&template=plugin_template.md&title=%5BPlugin%5D+THE+PLUGIN+NAME). This helps the community know what plugins are in development.
+If you start developing a plugin that you aim to release as open source, we suggest that you create a [new Issue](https://github.com/spotify/backstage/issues/new?labels=plugin&template=plugin_template.md&title=%5BPlugin%5D+THE+PLUGIN+NAME). This helps the community know what plugins are in development.
 
 You can also use this process if you have an idea for a good plugin but you hope that someone else will pick up the work.
 

docs/architecture-decisions/adr004-module-export-structure.md

@@ -23,7 +23,7 @@ We currently do not use any pattern for how to structure exports. There is a mix
 of package-level re-exports deep into the directory tree, shallow re-exports for
 each directory, exports using `*` and explicit lists of each symbol, etc. The
 mix and lack of predictability makes it difficult to reason about the boundaries
-of a module, and for example knowing whether is is safe to export a symbol in a
+of a module, and for example knowing whether it is safe to export a symbol in a
 given file.
 
 ## Decision

docs/plugins/index.md

@@ -9,7 +9,7 @@ Backstage is a single-page application composed of a set of plugins.
 Our goal for the plugin ecosystem is that the definition of a plugin is flexible
 enough to allow you to expose pretty much any kind of infrastructure or software
 development tool as a plugin in Backstage. By following strong
-[design guidelines](../dls/design.md) we ensure the the overall user experience
+[design guidelines](../dls/design.md) we ensure the overall user experience
 stays consistent between plugins.
 
 ![plugin](../assets/my-plugin_screenshot.png)

plugins/README.md

@@ -2,7 +2,7 @@
 
 Backstage is a single-page application composed of a set of plugins.
 
-Our goal for the plugin ecosystem is that the definition of a plugin is flexible enough to allow you to expose pretty much any kind of infrastructure or software development tool as a plugin in Backstage. By following strong [design guidelines](https://github.com/spotify/backstage/blob/master/docs/dls/design.md) we ensure the the overall user experience stays consistent between plugins.
+Our goal for the plugin ecosystem is that the definition of a plugin is flexible enough to allow you to expose pretty much any kind of infrastructure or software development tool as a plugin in Backstage. By following strong [design guidelines](https://github.com/spotify/backstage/blob/master/docs/dls/design.md) we ensure the overall user experience stays consistent between plugins.
 
 ![plugin](../docs/assets/my-plugin_screenshot.png)
 
@@ -12,6 +12,6 @@ To create a plugin, follow the steps outlined [here](https://github.com/spotify/
 
 ## Suggesting a plugin
 
-If you start developing a plugin that you aim to release as open source, we suggest that you create a new [new Issue](https://github.com/spotify/backstage/issues/new?template=plugin_template.md). This helps the community know what plugins are in development.
+If you start developing a plugin that you aim to release as open source, we suggest that you create a [new Issue](https://github.com/spotify/backstage/issues/new?template=plugin_template.md). This helps the community know what plugins are in development.
 
 You can also use this process if you have an idea for a good plugin but you hope that someone else will pick up the work.