Update methods.md (#3548)

resolves #3549

## What are you changing in this pull request and why?

This PR adds the (undocumented!) `resource_type` method that has been
possible for a long, long time.

Reason: we discovered a selection method wasn't documented! So we did 😎 

## Not done

#3549 mentions that there are no examples for the wildcard method that
include `wildcard:`. This seems okay since the intent in
dbt-labs/dbt-core#6599 was to use Unix-style
wildcards in conjunction with all the other selection methods.

So we're choosing not to add `wildcard:` examples in this PR. If needed,
they can always be added later.

## 🎩 


[Preview](https://deploy-preview-3548--docs-getdbt-com.netlify.app/reference/node-selection/methods#the-resource_type-method)

<img width="550" alt="image"
src="https://github.com/dbt-labs/docs.getdbt.com/assets/44704949/c46f18c5-d4ea-4e9a-815d-7f682efa4ee2">


## Checklist
- [x] Review the [Content style
guide](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/content-style-guide.md)
and [About
versioning](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#adding-a-new-version)
so my content adheres to these guidelines.

---------

Co-authored-by: mirnawong1 <[email protected]>
Co-authored-by: Doug Beatty <[email protected]>

website/docs/reference/node-selection/methods.md

@@ -46,6 +46,13 @@ The `source` method is used to select models that select from a specified [sourc
   $ dbt run --select source:snowplow+    # run all models that select from Snowplow sources
   ```
 
+### The "resource_type" method
+Use the `resource_type` method to select nodes of a particular type (`model`, `source`, `exposure`, etc). This is similar to the `--resource-type` flag used by the [`dbt ls` command](/reference/commands/list).
+
+  ```bash
+  $ dbt build --select resource_type:exposure    # build all resources upstream of exposures
+  $ dbt list --select resource_type:test    # list all tests in your project
+  ```
 
 ### The "path" method
 The `path` method is used to select models/sources defined at or under a specific path.
@@ -72,6 +79,7 @@ The `file` or `fqn` method can be used to select a model by its filename, includ
 
 ```bash
 # These are equivalent
+dbt run --select file:some_model.sql
 dbt run --select some_model.sql
 dbt run --select some_model
 dbt run --select fqn:some_model # fqn is an abbreviation for "fully qualified name"
@@ -335,4 +343,4 @@ dbt list --select access:private       # list all private models
 dbt list --select access:protected       # list all protected models
 ```
 
-</VersionBlock>
+</VersionBlock>