Updated "urlskip": positional lookup + example, also base64 example

Static-filter-syntax.md

@@ -1033,6 +1033,8 @@ The syntax is `urlskip=[steps]`, where steps is a space-separated list of extrac
 Valid directives:
 
 - `?name`: the value of parameter named `name` will be extracted and replace the current URL as the new URL
+- `&i` ([dev build 1.60.1b6+](https://github.com/gorhill/uBlock/commit/64b2086ba4)): meant to lookup a parameter's name at position `i` (1-based). The parameter name will be used as the
+URL (whereas `?` is meant to lookup a parameter's value)
 - `+https`: the protocol of the current URL will be forced to `https:`<br>
   This directive will succeed only if the protocol of the current URL is either absent or matches `http:` or `https:`
 - `-base64` ([dev build 1.61.1+](https://github.com/gorhill/uBlock/commit/e81e70937f5b6f8f98bdd8e6f71af030486efab8)): decode as a base64-encoded string
@@ -1056,6 +1058,19 @@ The above filter will cause navigation to `https://example.com/path/to/tracker?u
 
 _Note:_ No skip will occur if not all extraction directives can be fulfilled in a given URL. For example, `https://example.com/path/to/tracker?url=https%3A%2F%2Fexample.org%2Fpath%2Fto%2Ftracker` won't be skipped by the filter above because the `?to` step can't be fulfilled.
 
+```adb
+||shrinkearn.com/full?$urlskip=?url -base64
+```
+
+The above filter will decode `base64` encoded URL in `urlskip=` in example link `https://shrinkearn.com/full?api=3dd1f43f5fded450a0e4691e503bf19b31f35f44&url=aHR0cHM6Ly9rcmFrZW5maWxlcy5jb20vdmlldy9zamJ1RmpQVTF2L2ZpbGUuaHRtbA==&type=2`.
+
+```adb
+||pixiv.net/jump.php?$urlskip=&1
+```
+
+The above filter will lookup a parameter's name at given position in example link: `https://www.pixiv.net/jump.php?https%3A%2F%2Fx.com%2FExample_Username`, the parameter name will be used as the
+URL (whereas `?` is meant to lookup a parameter's value).
+
 <details><summary>Technical notes</summary>
 
 First commit in [1.59.1b22](https://github.com/gorhill/uBlock/commit/266ec4894b).