FINERACT-2269: various small dev-focused improvements

remove unnecessary javadoc html5 option

html5 output is the default since at least Java 17

improve markdown formatting for PR template

fix casing, per GH recommendations

https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/creating-a-pull-request-template-for-your-repository recommends lowercase

document system default Java issues

reorder integration test hints importance-wise

make devRun the default

It's faster and more obviously useful for developers.

See https://lists.apache.org/thread/zxvtx9nqqbojvt0dd65tk8zd4xp6ot0t

mention gradle not re-running tests

remove Gitpod

per James, Ádám, and Victor, this is no longer used/supported

for setting up a local dev environment see the top-level README.md and https://fineract-academy.com

.github/pull_request_template.md

@@ -0,0 +1,18 @@
+## Description
+
+Describe the changes made and why they were made.
+
+Ignore if these details are present on the associated [Apache Fineract JIRA ticket](https://github.com/apache/fineract/pull/1284).
+
+## Checklist
+
+Please make sure these boxes are checked before submitting your pull request - thanks!
+
+- [ ] Write the commit message as per https://github.com/apache/fineract/#pull-requests
+- [ ] Acknowledge that we will not review PRs that are not passing the build _("green")_ - it is your responsibility to get a proposed PR to pass the build, not primarily the project's maintainers.
+- [ ] Create/update unit or integration tests for verifying the changes made.
+- [ ] Follow coding conventions at https://cwiki.apache.org/confluence/display/FINERACT/Coding+Conventions.
+- [ ] Add required Swagger annotation and update API documentation at fineract-provider/src/main/resources/static/legacy-docs/apiLive.htm with details of any API changes
+- [ ] Submission is not a "code dump".  (Large changes can be made "in repository" via a branch.  Ask on the developer mailing list for guidance, if required.)
+
+FYI our guidelines for code reviews are at https://cwiki.apache.org/confluence/display/FINERACT/Code+Review+Guide.