runner update from old docs (#145)

* runner update from old docs

* split lines to make it easier to read

* remove backticks from titles

Author: rosieyohannan

docs/guides/modules/execution-runner/pages/machine-runner-3-configuration-reference.adoc

@@ -24,30 +24,37 @@ logging:
 
 NOTE: Machine runner can also be configured via environment variables. These will be prioritized over the YAML file, if set.
 
+---
+
 [#api-auth-token]
-=== `api.auth_token`
+=== api.auth_token
 
 `$CIRCLECI_RUNNER_API_AUTH_TOKEN`
 
 The token is used to identify the machine runner to CircleCI and can be generated by the xref:toolkit:local-cli.adoc[CircleCI CLI]. An existing token may be shared among many installations, but this token only allows a particular `resource_class` to be specified.
 
+---
+
 [#api-url]
-=== `api.url`
+=== api.url
 
 `$CIRCLECI_RUNNER_API_URL`
 
 The URL will be pointing to `https://runner.circleci.com` by default. It should not be modified unless you have a CircleCI server installation. In that case, it must be set to the URL of your server installation.
 
+---
+
 [#runner-name]
-=== `runner.name`
+=== runner.name
 
 `$CIRCLECI_RUNNER_NAME`
 
 `RUNNER_NAME` is a unique name of your choosing assigned to this particular machine runner. CircleCI recommends using the hostname of the machine so that it can be used to identify the agent when viewing statuses and job results in the CircleCI web app. The only special characters accepted in `RUNNER_NAME` are `. () - _`.
 
+---
 
 [#logging-level]
-=== `logging.level`
+=== logging.level
 
 `$CIRCLECI_RUNNER_LOGGING_LEVEL`
 
@@ -60,9 +67,10 @@ logging:
   level: "info"
 ```
 
+---
 
 [#logging-format]
-=== `logging.format`
+=== logging.format
 
 `$CIRCLECI_RUNNER_LOGGING_FORMAT`
 
@@ -80,9 +88,10 @@ logging:
   format: "color"
 ```
 
+---
 
 [#logging-file]
-=== `logging.file`
+=== logging.file
 
 `$CIRCLECI_RUNNER_LOGGING_FILE`
 
@@ -95,9 +104,10 @@ logging:
   file: "-"
 ```
 
+---
 
 [#runner-task-agent-directory]
-=== `runner.task_agent_directory`
+=== runner.task_agent_directory
 
 `$CIRCLECI_RUNNER_TASK_AGENT_DIRECTORY`
 
@@ -108,9 +118,10 @@ runner:
   task_agent_directory: "~/.local/libexec/circleci"
 ```
 
+---
 
 [#runner-command-prefix]
-=== `runner.command_prefix`
+=== runner.command_prefix
 
 `$CIRCLECI_RUNNER_COMMAND_PREFIX`
 
@@ -151,8 +162,10 @@ runner:
   command_prefix: ["/var/opt/circleci/wrapper.sh"]
 ```
 
+---
+
 [#runner-working-directory]
-=== `runner.working_directory`
+=== runner.working_directory
 
 `$CIRCLECI_RUNNER_WORK_DIR`
 
@@ -169,8 +182,10 @@ runner:
   working_directory: "/var/lib/circleci-runner/workdir"
 ```
 
+---
+
 [#runner-cleanup-working-directory]
-=== `runner.cleanup_working_directory`
+=== runner.cleanup_working_directory
 `$CIRCLECI_RUNNER_CLEANUP_WORK_DIR`
 
 This flag enables you to control the working directory cleanup after each job.
@@ -189,8 +204,10 @@ runner:
   cleanup_working_directory: true
 ```
 
+---
+
 [#runner-use-ssh-dir-for-checkout-keys]
-=== `runner.use_home_ssh_dir_for_checkout_keys`
+=== runner.use_home_ssh_dir_for_checkout_keys
 `$USE_HOME_SSH_DIR_FOR_CHECKOUT_KEYS`
 
 This flag enables you to use the home directory of the user running the self-hosted runner instance for storing SSH checkout keys.
@@ -209,8 +226,10 @@ runner:
    use_home_ssh_dir_for_checkout_keys: true
 ```
 
+---
+
 [#runner-mode]
-=== `runner.mode`
+=== runner.mode
 
 `$CIRCLECI_RUNNER_MODE`
 
@@ -249,8 +268,26 @@ runner:
   mode: single-task
 ```
 
+---
+
+[#cache-task-agent]
+=== runner.cache_task_agent
+
+`$CIRCLECI_RUNNER_CACHE_TASK_AGENT`
+
+When set to true, machine runner will not clear the task-agent cache when the agent shuts down. On startup the machine agent will check for an already downloaded task agent and will use that task-agent unless there is a newer version of task-agent available for download. This feature is off by default. This may be particularly useful for Windows which relies on `single-task` mode.
+
+Example:
+
+```yaml
+runner:
+  cache_task_agent: true
+```
+
+---
+
 [#runner-max-run-time]
-=== `runner.max_run_time`
+=== runner.max_run_time
 
 `$CIRCLECI_RUNNER_MAX_RUN_TIME`
 
@@ -285,8 +322,10 @@ Draining can end in one of two ways:
 * The task has been in the draining state for longer than the configured `max_run_time`
 * An additional TERM signal is received by the machine runner during _draining_
 
+---
+
 [#runner-idle-timeout]
-=== `runner.idle_timeout`
+=== runner.idle_timeout
 `$CIRCLECI_RUNNER_IDLE_TIMEOUT`
 
 This timeout will enable a machine runner to terminate if no task has been claimed within the given time period. The value is a string with the following unit identifiers: `h`, `m` or `s` for hours, minutes, and seconds respectively (for example, `5m` is 5 minutes).
@@ -300,8 +339,10 @@ runner:
   idle_timeout: 1h
 ```
 
+---
+
 [#runner-ssh-advertise-addr]
-=== `runner.ssh.advertise_addr`
+=== runner.ssh.advertise_addr
 `$CIRCLECI_RUNNER_SSH_ADVERTISE_ADDR`
 
 This parameter enables the “Rerun job with SSH” feature. Before enabling this feature, there are <<#considerations-before-enabling-ssh-debugging,*important considerations*>> that should be made. Rerun with SSH is not currently available on container runner.
@@ -328,6 +369,8 @@ Task-agent runs an embedded SSH server and agent on a dedicated port when the 
 * The SSH server is configured for public key authentication. Anyone with permission to initiate a job can rerun it with SSH. However, only the user who initiated the rerun will have their SSH public keys added to the server for the duration of the SSH session.
 * Rerunning a job with SSH will hold the job open for *two hours* if a connection is made to the SSH server, or *ten minutes* if no connection is made, unless cancelled. While in this state, the job is counted against an organization’s concurrency limit, and the task-agent will be unavailable to handle other jobs. Therefore, it is recommended to cancel an SSH rerun job explicitly (through the web UI or CLI) when finished debugging.
 
+---
+
 [#basic-full-configuration-for-machine-runner]
 === Basic full configuration for a machine runner