feat: add revisions for all levels as query param

Closes #20

content/page/specs.md

@@ -118,13 +118,9 @@ Returns an [item object](#item-object).
 
 `https://{server}{/prefix}/items/{item}`
 
-
-
 #### Examples
 
 * `https://example.com/textapi/items/p2`
-* `https://example.com/textapi/items/p2?revision=2.0.1`
-* `https://example.com/textapi/manifests/Othello/full?revision=1.2.0`
 
 ## Schema
 
@@ -141,6 +137,8 @@ It is REQUIRED to be served at the corresponding [endpoint](#collection).
 |----|----|----|----|
 | @context | 1 | URL | the JSON-LD context of this object. MUST be `https://gitlab.gwdg.de/subugoe/textapi/specs/-/raw/main/jsonld/collection.jsonld` |
 | textapi | 1 | semver | the TextAPI version covered by the implementation |
+| revision | 1 | string | the revision of the Collection Object, e.g. a hash, a number, a timestamp or any other version string |
+| prevRevision | ? | URL | reference to the previous revision of the Collection Object | 
 | id | 1 | URL | URL pointing to this collection |
 | title | 1 | \[[Title Object](#title-object)\] | the title of the collection. the main title `MUST` be the first one in the array |
 | collector | 1 | \[[Actor Object](#actor-object)\] | a personal entity responsible for the collection (collector) |
@@ -188,6 +186,8 @@ It is REQUIRED to be served at the corresponding [endpoint](#manifest).
 |----|----|----|----|
 | @context | 1 | URL | the JSON-LD context of this object. MUST be `https://gitlab.gwdg.de/subugoe/textapi/specs/-/raw/main/jsonld/manifest.jsonld` |
 | textapi | 1 | semver | version number satisfied by the implementation |
+| revision | 1 | string | the revision of the Manifest Object, e.g. a hash, a number, a timestamp or any other version string |
+| prevRevision | ? | URL | reference to the previous revision of the Manifest Object |
 | id | 1 | URL | URL pointing to this manifest |
 | label | 1 | string | human-readable name or title |
 | sequence | 1 | \[[Sequence Object](#sequence-object)\] | a sequence of `items` |
@@ -284,6 +284,8 @@ Any other (sliced) material is either a `section` or a `page`.
 |----|----|----|----|
 | @context | 1 | URL | the JSON-LD context of this object. MUST be `https://gitlab.gwdg.de/subugoe/textapi/specs/-/raw/main/jsonld/item.jsonld` |
 | textapi | 1 | semver | version number satisfied by the implementation |
+| revision | 1 | string | the revision of the Item Object, e.g. a hash, a number, a timestamp or any other version string |
+| prevRevision | ? | URL | reference to the previous revision of the Item Object |
 | id | 1 | URL | URL pointing to this item |
 | title | ? | \[[Title Object](#title-object)\] | the title of the item. the main title `MUST` be the first one in the array |
 | type | 1 | string | one of `section`, `page`, `full` |