docs: Fix minor link wording woes [skip ci] (#12024)

* Fix design/monorepo.md DO blog link [skip ci]

* Fix README signup wording [skip ci]

* Update README link [skip ci]

* Fix CONTRIBUTING signup wording [skip ci]

* Fix CONTRIBUTING Slack link [skip ci]

CONTRIBUTING.md

@@ -28,14 +28,14 @@ If you want an already configured online IDE to contribute to Babel, you can use
   - Check out [the Babel Plugin Handbook](https://github.com/thejameskyle/babel-handbook/blob/master/translations/en/plugin-handbook.md#babel-plugin-handbook) - core plugins are written the same way as any other plugin!
   - Check out [AST Explorer](http://astexplorer.net/#/scUfOmVOG5) to learn more about ASTs or make your own plugin in the browser
 - When you feel ready to jump into the Babel source code, a good place to start is to look for issues tagged with [help wanted](https://github.com/babel/babel/labels/help%20wanted) and/or [good first issue](https://github.com/babel/babel/labels/good%20first%20issue).
-- Follow along with what we are working on by joining our [Slack](https://babeljs.slack.com) (you can sign-up [here](https://slack.babeljs.io/)
+- Follow along with what we are working on by joining our [Slack](https://babeljs.slack.com) (you can [sign up here](https://slack.babeljs.io/)
   for an invite), following our announcements on [Twitter](https://twitter.com/babeljs), and reading (or participating!) in our [meeting notes](https://github.com/babel/notes).
 - Check out our [website](http://babeljs.io/) and the [repo](https://github.com/babel/website)
 - You can contribute by triaging issues which may include reproducing bug reports or asking for vital information, such as version numbers or reproduction instructions. If you would like to start triaging issues, one easy way to get started is to [subscribe to babel on CodeTriage](https://www.codetriage.com/babel/babel). [![Open Source Helpers](https://www.codetriage.com/babel/babel/badges/users.svg)](https://www.codetriage.com/babel/babel)
 
 ## Chat
 
-Feel free to check out the `#discussion`/`#development` channels on our [Slack](https://slack.babeljs.io) (you can sign-up [here](https://slack.babeljs.io/) for an invite). Some of us are always online to chat!
+Feel free to check out the `#discussion`/`#development` channels on our [Slack](https://babeljs.slack.com) (you can [sign up here](https://slack.babeljs.io/) for an invite). Some of us are always online to chat!
 
 ## Developing
 

README.md

@@ -91,7 +91,7 @@ I'm so glad you asked: [Hallelujah —— In Praise of Babel](SONG.md) by [@angu
 
 ### Looking for support?
 
-For questions and support please join our [Slack Community](https://slack.babeljs.io/) (you can sign-up [here](https://slack.babeljs.io/) for an invite), ask a question on [Stack Overflow](https://stackoverflow.com/questions/tagged/babeljs), or ping us on [Twitter](https://twitter.com/babeljs).
+For questions and support please join our [Slack Community](https://slack.babeljs.io/) (you can [sign up here](https://slack.babeljs.io/) for an invite), ask a question on [Stack Overflow](https://stackoverflow.com/questions/tagged/babeljs), or ping us on [Twitter](https://twitter.com/babeljs).
 
 ### Where are the docs?
 
@@ -105,7 +105,7 @@ Please read through our [CONTRIBUTING.md](CONTRIBUTING.md) and fill out the issu
 
 Check out:
 
-- Our [#development](https://babeljs.slack.com/messages/development) Slack channel and say hi ([signup](https://slack.babeljs.io))!
+- Our [#development](https://babeljs.slack.com/messages/development) Slack channel and say hi! ([sign-up](https://slack.babeljs.io))
 - Issues with the [good first issue](https://github.com/babel/babel/labels/good%20first%20issue) and [help wanted](https://github.com/babel/babel/labels/help%20wanted) label. We suggest also looking at the [closed ones](https://github.com/babel/babel/issues?utf8=%E2%9C%93&q=is%3Aclosed+label%3A%22good+first+issue%22) to get a sense of the kinds of issues you can tackle.
 
 Some resources:

doc/design/monorepo.md

@@ -37,7 +37,7 @@ This is quite taboo but let's look at the pros and cons:
 - [Benjamin Pollack](http://bitquabit.com/post/unorthodocs-abandon-your-dvcs-and-return-to-sanity/)
 - [Benjamin Eberlei](https://qafoo.com/resources/presentations/froscon_2015/monorepos.html)
 - [Simon Stewart](http://blog.rocketpoweredjetpants.com/2015/04/monorepo-one-source-code-repository-to.html)
-- [Digital Ocean](https://www.digitalocean.com/company/blog/taming-your-go-dependencies/)
+- [Digital Ocean](https://www.digitalocean.com/blog/taming-your-go-dependencies/)
 - [Google](http://www.infoq.com/presentations/Development-at-Google), [another](https://www.youtube.com/watch?v=W71BTkUbdqE)
 - [Twitter](https://www.youtube.com/watch?v=bjh4DHuOf4E)
 - [thedufer](http://www.reddit.com/r/programming/comments/1unehr/scaling_mercurial_at_facebook/cek9nkq)