Update HikariCP to 4.0.3

Update json4s-jackson to 3.6.11 (#2699)

Update auto_update.md

Update build.md

Update jetty-continuation, jetty-http, ... to 9.4.38.v20210224

Update github-api to 1.123

Update oauth2-oidc-sdk to 9.2.1

ignore jetty 11.x and 10.x updates

Update testcontainers-scala to 0.39.3 (#2695)

Update README.md (#2694) ...

## Developer information is hard to find

I've been looking for instructions on how to build gitbucket a couple of times, and I've never found them until takzoe pointed me towards `doc/build.md`. After knowing about this, I read through the readme once again, looking for such a link, and then I've found it as the last sentence within a section named `Features`.

What I've been looking for:
 - either a file named `INSTALL.md`, `BUILD.md` in `/`
 - or a section (or a link) in the main readme

I've put the link to `doc/readme.md` into a separate section "Building and Development" and added a short summary. I'm not so sure about the order of the new section and "Plugins".

Update testcontainers-scala to 0.39.2 (#2693)

Update scala-library to 2.13.5

Update oauth2-oidc-sdk to 9.2

Update jetty-continuation, jetty-http, ... to 9.4.37.v20210219

Update mockito-core to 3.8.0

updates.includeScala = true

Add create and push webhooks call for branch creation via GUI. (#2624)

Links to files and lines in the diff view (#2685)

Prevent execution of empty SQL strings during database import (#2664) ...

Co-authored-by: Naoki Takezoe <takezoe@gmail.com>

Update authenticator.md

Fix issue / pull request view templates (#2684)

Upgrade java-diff-utils (#2678)

Update postgresql to 42.2.19 (#2682)

Update commons-net to 3.8.0 (#2683)

Update authenticator.md

Update authenticator.md

Fix typo

Fix typo

use slash syntax instead of old "in" ...

https://github.com/sbt/sbt/pull/6309

Update sbt-pgp to 2.1.2 (#2681) ...

Co-authored-by: Naoki Takezoe <takezoe@gmail.com>