release: bump 0.8.7 -> 0.8.8 (#265)

Version bump `0.8.7` → `0.8.8`.

### Fixed
- R binding: declare `Depends: R (>= 2.10)`, clearing the `R CMD check` "package needs dependence on R (>= 2.10)" warning that the bundled, lazy-loaded `sample_ohlcv` dataset triggers on r-universe / CRAN. (#264)

Bump touches the manual release touchpoints only; docs/webpage version strings are left to `sync-about.yml` on the tag.

examples/java/pom.xml

@@ -6,7 +6,7 @@
 
   <groupId>org.wickra.examples</groupId>
   <artifactId>wickra-examples</artifactId>
-  <version>0.8.7</version>
+  <version>0.8.8</version>
   <packaging>jar</packaging>
 
   <name>Wickra Java examples</name>
@@ -21,7 +21,7 @@
     <dependency>
       <groupId>org.wickra</groupId>
       <artifactId>wickra</artifactId>
-      <version>0.8.7</version>
+      <version>0.8.8</version>
     </dependency>
     <!-- Only the network examples (fetch_btcusdt) parse JSON. -->
     <dependency>