Add ability to copy a permalink to a line (#7119)

This PR adds the ability to copy the permalink to a line from within
Zed.

This functionality is available through the `editor: copy permalink to
line` action in the command palette:

<img width="589" alt="Screenshot 2024-01-30 at 7 07 46 PM"
src="https://github.com/zed-industries/zed/assets/1486634/332282cb-211f-4f16-9eb1-415bcfee9b7b">

Executing this action will create a permalink to the currently selected
line(s) and copy it to the clipboard.

Here is an example line:

```
https://github.com/maxdeviant/auk/blob/56c80e80112744740be1969c89fdd34db4be6f64/src/lib.rs#L25
```

Currently, both GitHub and GitLab are supported.

### Notes and known limitations

- In order to determine where to permalink to, we read the URL of the
`origin` remote in Git. This feature will not work if the `origin`
remote is not present.
- Attempting to permalink to a ref that is not pushed to the origin will
result in the link 404ing.
- Attempting to permalink when Git is in a dirty state may not generate
the right link.
- For instance, modifying a file (e.g., adding new lines) and grabbing a
permalink to it will result in incorrect line numbers.

Release Notes:

- Added the ability to copy a permalink to a line
([#6777](https://github.com/zed-industries/zed/issues/6777)).
- Available via the `editor: copy permalink to line` action in the
command palette.

Cargo.toml

@@ -132,6 +132,7 @@ tree-sitter = { version = "0.20" }
 unindent = { version = "0.1.7" }
 pretty_assertions = "1.3.0"
 git2 = { version = "0.15", default-features = false}
+url = "2.2"
 uuid = { version = "1.1.2", features = ["v4"] }
 
 tree-sitter-bash = { git = "https://github.com/tree-sitter/tree-sitter-bash", rev = "7331995b19b8f8aba2d5e26deb51d2195c18bc94" }