### What changes were proposed in this pull request?
Change the link to the Scala API document.
```
$ git grep "#org.apache.spark.package"
docs/_layouts/global.html: <li><a href="api/scala/index.html#org.apache.spark.package">Scala</a></li>
docs/index.md:* [Spark Scala API (Scaladoc)](api/scala/index.html#org.apache.spark.package)
docs/rdd-programming-guide.md:[Scala](api/scala/#org.apache.spark.package), [Java](api/java/), [Python](api/python/) and [R](api/R/).
```
### Why are the changes needed?
The home page link for Scala API document is incorrect after upgrade to 3.0
### Does this PR introduce any user-facing change?
Document UI change only.
### How was this patch tested?
Local test, attach screenshots below:
Before:
After:
Closes#27549 from xuanyuanking/scala-doc.
Authored-by: Yuanjian Li <xyliyuanjian@gmail.com>
Signed-off-by: Sean Owen <srowen@gmail.com>
## What changes were proposed in this pull request?
Add AL2 license to metadata of all .md files.
This seemed to be the tidiest way as it will get ignored by .md renderers and other tools. Attempts to write them as markdown comments revealed that there is no such standard thing.
## How was this patch tested?
Doc build
Closes#24243 from srowen/SPARK-26918.
Authored-by: Sean Owen <sean.owen@databricks.com>
Signed-off-by: Sean Owen <sean.owen@databricks.com>
## What changes were proposed in this pull request?
Fix Typos.
This PR is the complete version of https://github.com/apache/spark/pull/23145.
## How was this patch tested?
NA
Closes#23185 from kjmrknsn/docUpdate.
Authored-by: Keiji Yoshida <kjmrknsn@gmail.com>
Signed-off-by: Sean Owen <sean.owen@databricks.com>
