docs: Various updates for 2.3, 2.4 beta, and Go 1.16

Steps on #139 (sorry)

src/docs/markdown/caddyfile/directives/abort.md

@@ -0,0 +1,22 @@
+---
+title: abort (Caddyfile directive)
+---
+
+# abort
+
+Prevents any response to the client by immediately aborting the HTTP handler chain and closing the connection. Any concurrent, active HTTP streams on the same connection are interrupted.
+
+
+## Syntax
+
+```caddy-d
+abort [<matcher>]
+```
+
+## Examples
+
+Abort all requests for paths starting with `/foo`:
+
+```caddy-d
+abort /foo*
+```

src/docs/markdown/caddyfile/directives/acme_server.md

@@ -11,11 +11,16 @@ When enabled, requests matching the path `/acme/*` will be handled by the ACME s
 
 ## Client configuration
 
-Using ACME server defaults, ACME clients should simply be configured to use `https://localhost/acme/local/directory` as their ACME endpoint. (`local` is the name of Caddy's default CA.)
+Using ACME server defaults, ACME clients should simply be configured to use `https://localhost/acme/local/directory` as their ACME endpoint. (`local` is the ID of Caddy's default CA.)
 
 
 ## Syntax
 
 ```caddy-d
-acme_server [<matcher>]
+acme_server [<matcher>] {
+	ca <id>
+}
 ```
+
+- **ca** specifies the ID of the certificate authority with which to sign certificates. The default is `local`, which is Caddy's default CA, intended for locally-used, self-signed certificates, which is most common in dev environments. For broader use, it is recommended to specify a different CA to avoid confusion. If the CA with the given ID does not already exist, it will be created.
+

src/docs/markdown/caddyfile/directives/tls.md

@@ -107,6 +107,7 @@ Obtains certificates using the ACME protocol.
 	test_dir <test_directory_url>
 	email    <email>
 	timeout  <duration>
+	key_type ed25519|p256|p384|rsa2048|rsa4096
 	disable_http_challenge
 	disable_tlsalpn_challenge
 	alt_http_port    <port>
@@ -122,6 +123,7 @@ Obtains certificates using the ACME protocol.
 - **test_dir** is an optional fallback directory to use when retrying challenges; if all challenges fail, this endpoint will be used during retries; useful if a CA has a staging endpoint where you want to avoid rate limits on their production endpoint. Default: `https://acme-staging-v02.api.letsencrypt.org/directory`
 - **email** is the ACME account contact email address.
 - **timeout** is how long to wait before timing out an ACME operation.
+- **key_type** is the type of key to use when generating CSRs. Only set this if you have a specific requirement.
 - **disable_http_challenge** will disable the HTTP challenge.
 - **disable_tlsalpn_challenge** will disable the TLS-ALPN challenge.
 - **alt_http_port** is an alternate port on which to serve the HTTP challenge; it has to happen on port 80 so you must forward packets to this alternate port.