feat: URL preview support

from upstream MR https://gitlab.com/famedly/conduit/-/merge_requests/347
with the following changes (so far):
- remove hardcoded list of allowed hosts (strongly disagree with this,
even if it is desired, it should not be harcoded)
- add more allow config options for granularity via URL contains,
host contains, and domain is (explicit match) for security
- warn if a user is allowing all URLs to be previewed for security reasons
- replace an expect with proper error handling
- bump webpage to 2.0
- improved code style a tad

Co-authored-by: rooot <hey@rooot.gay>
Signed-off-by: rooot <hey@rooot.gay>
Signed-off-by: strawberry <strawberry@puppygock.gay>

Cargo.toml

@@ -91,7 +91,7 @@ hmac = "0.12.1"
 sha-1 = "0.10.1"
 sha2 = { version = "0.10.8" }
 # used for conduit's CLI and admin room command parsing
-clap = { version = "4.4.17", default-features = false, features = ["std", "derive", "help", "usage", "error-context"] }
+clap = { version = "4.5.0", default-features = false, features = ["std", "derive", "help", "usage", "error-context"] }
 futures-util = { version = "0.3.30", default-features = false }
 # Used for reading the configuration from conduit.toml & environment variables
 figment = { version = "0.10.14", features = ["env", "toml"] }
@@ -106,6 +106,8 @@ ipaddress = "0.1.3"
 
 sd-notify = { version = "0.4.1", optional = true }
 
+webpage = { version = "2.0", default-features = false }
+
 [target.'cfg(unix)'.dependencies]
 nix = { version = "0.27.1", features = ["resource"] }