docs: correct grammar mistakes in CONTRIBUTING.md (angular#22285)

Various grammar mistakes were present in the contribution guidelines
This commit corrects some of them

PR Close angular#22285

CONTRIBUTING.md

@@ -51,7 +51,7 @@ and help you to craft the change so that it is successfully accepted into the pr
 
 Before you submit an issue, please search the issue tracker, maybe an issue for your problem already exists and the discussion might inform you of workarounds readily available.
 
-We want to fix all the issues as soon as possible, but before fixing a bug we need to reproduce and confirm it. In order to reproduce bugs we will systematically ask you to provide a minimal reproduction scenario using http://plnkr.co. Having a live, reproducible scenario gives us wealth of important information without going back & forth to you with additional questions like:
+We want to fix all the issues as soon as possible, but before fixing a bug we need to reproduce and confirm it. In order to reproduce bugs, we will systematically ask you to provide a minimal reproduction scenario using http://plnkr.co. Having a live, reproducible scenario gives us a wealth of important information without going back & forth to you with additional questions like:
 
 - version of Angular used
 - 3rd-party libraries and their versions
@@ -61,7 +61,7 @@ A minimal reproduce scenario using http://plnkr.co/ allows us to quickly confirm
 
 We will be insisting on a minimal reproduce scenario in order to save maintainers time and ultimately be able to fix more bugs. Interestingly, from our experience users often find coding problems themselves while preparing a minimal plunk. We understand that sometimes it might be hard to extract essentials bits of code from a larger code-base but we really need to isolate the problem before we can fix it.
 
-Unfortunately we are not able to investigate / fix bugs without a minimal reproduction, so if we don't hear back from you we are going to close an issue that don't have enough info to be reproduced.
+Unfortunately, we are not able to investigate / fix bugs without a minimal reproduction, so if we don't hear back from you we are going to close an issue that doesn't have enough info to be reproduced.
 
 You can file new issues by filling out our [new issue form](https://github.com/angular/angular/issues/new).
 
@@ -173,12 +173,12 @@ The **header** is mandatory and the **scope** of the header is optional.
 Any line of the commit message cannot be longer 100 characters! This allows the message to be easier
 to read on GitHub as well as in various git tools.
 
-Footer should contain a [closing reference to an issue](https://help.github.com/articles/closing-issues-via-commit-messages/) if any.
+The footer should contain a [closing reference to an issue](https://help.github.com/articles/closing-issues-via-commit-messages/) if any.
 
 Samples: (even more [samples](https://github.com/angular/angular/commits/master))
 
 ```
-docs(changelog): update change log to beta.5
+docs(changelog): update changelog to beta.5
 ```
 ```
 fix(release): need to depend on latest rxjs and zone.js
@@ -203,7 +203,7 @@ Must be one of the following:
 * **test**: Adding missing tests or correcting existing tests
 
 ### Scope
-The scope should be the name of the npm package affected (as perceived by person reading changelog generated from commit messages.
+The scope should be the name of the npm package affected (as perceived by the person reading the changelog generated from commit messages.
 
 The following is the list of supported scopes:
 
@@ -232,10 +232,10 @@ There are currently a few exceptions to the "use package name" rule:
 * none/empty string: useful for `style`, `test` and `refactor` changes that are done across all packages (e.g. `style: add missing semicolons`)
 
 ### Subject
-The subject contains succinct description of the change:
+The subject contains a succinct description of the change:
 
 * use the imperative, present tense: "change" not "changed" nor "changes"
-* don't capitalize first letter
+* don't capitalize the first letter
 * no dot (.) at the end
 
 ### Body
@@ -266,7 +266,7 @@ changes to be accepted, the CLA must be signed. It's a quick process, we promise
   * https://help.github.com/articles/setting-your-commit-email-address-in-git/
   * https://stackoverflow.com/questions/37245303/what-does-usera-committed-with-userb-13-days-ago-on-github-mean
   * https://help.github.com/articles/about-commit-email-addresses/
-  * https://help.github.com/articles/blocking-command-line-pushes-that-expose-your-personal-email-address/ 
+  * https://help.github.com/articles/blocking-command-line-pushes-that-expose-your-personal-email-address/
 
   Note that if you have more than one Git identity, it is important to verify that you are logged in with the same ID with which you signed the CLA, before you commit changes. If not, your PR will fail the CLA check.