docs: improve manager documentation (#7738)

Co-authored-by: Jamie Magee <JamieMagee@users.noreply.github.com>

docs/usage/modules/manager.md

@@ -15,12 +15,12 @@ The goal of Renovate is to detect and maintain all third party dependencies in y
 ### File Matching
 
 Most managers have a default `fileMatch` array.
-`fileMatch` is an array of Regular Expression strings used to match against the repository file list.
+The `fileMatch` array contains regular expression strings that match against the repository file list.
 
 #### Managers with no default fileMatch
 
-Some managers have no default `fileMatch`, because they have no file naming convention that would let Renovate intelligently filter them.
-In such a case, the manager will be effectively disabled until you configure a `fileMatch` value, e.g. like the following:
+Some managers have no default `fileMatch` regular expression, because they have no filename convention that would let Renovate intelligently filter them.
+In such a case, the manager will be disabled until you create a `fileMatch` regular expression, e.g. like the following:
 
 ```json
 {
@@ -32,7 +32,7 @@ In such a case, the manager will be effectively disabled until you configure a `
 
 #### Extending a manager's default fileMatch
 
-If the default `fileMatch` value for a manager does not match against one of your relevant files, you can _extend_ the existing value(s) by configuring a manager's `fileMatch` like in this example:
+If the default `fileMatch` regular expression for a manager does not match against one of your relevant files, you can _extend_ the existing regular expression(s) by configuring a manager's `fileMatch` like in this example:
 
 ```json
 {
@@ -44,16 +44,18 @@ If the default `fileMatch` value for a manager does not match against one of you
 
 #### Ignoring files that match the default fileMatch
 
-Note: Renovate will _extend_ the existing `fileMatch`, meaning you don't need to include the default values like `Dockerfile` in your own array.
-In other words, the values are "additive". If a manager matches a file that you _don't_ want it to, ignore it using the `ignorePaths` configuration option.
-Also, if you ever find that Renovate is _not_ matching a file name that you're certain it should, be sure to check that you your preset config isn't the cause of it.
+Renovate will _extend_ the existing `fileMatch`, meaning you don't need to include the default regular expressions like `Dockerfile` in your own array.
+In other words, the regular expression are "additive".
+If a manager matches a file that you _don't_ want it to, ignore it using the `ignorePaths` configuration option.
+Also, if you ever find that Renovate is _not_ matching a file name that you're certain it should, check your preset config isn't the cause of it.
 The `config:base` preset ignores common test and example directory names, for example.
 
 ### Enabling and Disabling Managers
 
 #### Enabling experimental managers
 
-Most managers are enabled by default. For those that aren't - typically because they are considered experimental - you can opt-in to them like the following:
+Most managers are enabled by default.
+For those that aren't, typically because they are considered experimental, you can opt-in to them like the following:
 
 ```json
 {
@@ -85,11 +87,13 @@ To disable all managers within a language like `python`, do this:
 }
 ```
 
-Note: Only languages declared by a Renovate manager can be supported, so please verify first.
+Only languages declared by a Renovate manager are supported.
+Please check the [list of supported managers](https://docs.renovatebot.com/modules/manager/#supported-managers).
 
 #### Limiting enabled managers
 
-If you want to limit Renovate to only one or a small number of managers, you can do this with the `enabledManagers` array:
+Say you only want to use Renovate for JavaScript packages, and to update your Dockerfile, and don't want any other updates.
+You can use the `enabledManagers` array, to list the managers you want to use (`npm`, `dockerfile`):
 
 ```json
 {
@@ -97,4 +101,4 @@ If you want to limit Renovate to only one or a small number of managers, you can
 }
 ```
 
-The above would then result in all other managers being disabled, including Bundler, Composer, Docker Compose, etc.
+Using the `enabledManager` array disables all other managers, this includes Bundler, Composer, Docker Compose, etc.