Make example READMEs more consistent

examples/05-using-a-database/README.md

···
-# Wisp Example: Using A Database
+# Wisp Example: Using a database
 
 ```sh
 gleam run   # Run the server

examples/08-working-with-cookies/README.md

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 This example shows how to read and write cookies, and how to sign cookies so
 they cannot be tampered with.
 
-This example is based off of the [working with form data example][form-data] so read that one
+This example is based off of the ["working with form data" example][form-data] so read that one
 first. The additions are detailed here and commented in the code.
 
 Signing of cookies uses the `secret_key_base` value. If this value changes then

examples/09-configuring-default-responses/README.md

···
 
 You likely want your application to return a generic error page rather than an empty body, and this example shows how to do that.
 
-This example is based off of the [routing example][routing] so read that first.
+This example is based off of the ["routing" example][routing] so read that first.
 The additions are detailed here and commented in the code.
 
 [routing]: https://github.com/lpil/wisp/tree/main/examples/01-routing

examples/10-working-with-files/README.md

···
 
 This example shows how to accept file uploads and allow users to download files.
 
-This example is based off of the ["Working with form data" example][formdata], 
+This example is based off of the ["working with form data" example][formdata],
 so read that first. The additions are detailed here and commented in the code.
 
 [formdata]: https://github.com/lpil/wisp/tree/main/examples/02-working-with-form-data