documentation: fix typos in getting-started

| Typo           | Fix            |
| -------------- | -------------- |
| a an api       | an api         |
| adminsitrative | administrative |
| attemping      | attempting     |

[skip ci]
Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

Documentation/getting-started.md

@@ -55,13 +55,13 @@ The dex overlord and workers allow multiple key secrets (separated by commas) to
 
 # Generate an Admin API Secret
 
-The dex overlord has a an API which is very powerful - you can create Admin users with it, so it needs to be protected somehow. This is accomplished by requiring that a secret is passed via the Authorization header of each request. This secret is 128 bytes base64 encoded, and should be sufficiently random so as to make guessing impractical:
+The dex overlord has an API which is very powerful - you can create Admin users with it, so it needs to be protected somehow. This is accomplished by requiring that a secret is passed via the Authorization header of each request. This secret is 128 bytes base64 encoded, and should be sufficiently random so as to make guessing impractical:
 
 `DEX_OVERLORD_ADMIN_API_SECRET=$(dd if=/dev/random bs=1 count=128 2>/dev/null | base64 | tr -d '\n')`
 
 # Start the overlord
 
-The overlord is responsible for creating and rotating keys and some other adminsitrative tasks. In addition, the overlord is responsible for creating the necessary database tables (and when you update, performing schema migrations), so it must be started before we do anything else. Debug logging is turned on so we can see more of what's going on. Start it up.
+The overlord is responsible for creating and rotating keys and some other administrative tasks. In addition, the overlord is responsible for creating the necessary database tables (and when you update, performing schema migrations), so it must be started before we do anything else. Debug logging is turned on so we can see more of what's going on. Start it up.
 
 `./bin/dex-overlord --admin-api-secret=$DEX_OVERLORD_ADMIN_API_SECRET --db-url=$DEX_DB_URL --key-secrets=$DEX_KEY_SECRET --log-debug=true &`
 
@@ -161,4 +161,4 @@ In a fully configured production environment an email provider will be set up so
 
 # Standup Dev Script
 
-A script which does almost everything in this guide exists at `contrib/standup-db.sh`. Read the comments inside before attemping to run it - it requires a little setup beforehand.
+A script which does almost everything in this guide exists at `contrib/standup-db.sh`. Read the comments inside before attempting to run it - it requires a little setup beforehand.