use new github issue forms for build-failure and sandbox-limits templates

Author: syphar

.github/ISSUE_TEMPLATE/crate-build-failure.md

@@ -0,0 +1,25 @@
+---
+name: Crate build failure
+description: My crate failed to build in docs.rs.
+labels: build-failure
+body:
+  - type: markdown
+    attributes:
+      value: |
+        If you need a system dependency added for your crate to build,
+        consider making a PR to https://github.com/rust-lang/crates-build-env
+        instead of opening an issue here. There are detailed instructions for
+        this at https://forge.rust-lang.org/docs-rs/add-dependencies.html.
+  - type: input
+    attributes:
+      label: crate name
+    validations:
+      required: true
+  - type: input
+    attributes:
+      label: build failure link
+    validations:
+      required: true
+  - type: textarea
+    attributes:
+      label: additional details

.github/ISSUE_TEMPLATE/crate-build-failure.yaml

@@ -0,0 +1,33 @@
+---
+name: Sandbox limits increase request
+description: My crate build won't complete within the sandbox limits.
+labels: limits-increase
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Please note we *won't* enable network access or allow
+        the crate to write in read-only directories, to avoid
+        compromising the security of docs.rs itself.
+  - type: input
+    attributes:
+      label: crate name
+    validations:
+      required: true
+  - type: input
+    attributes:
+      label: build failure link
+    validations:
+      required: true
+  - type: input
+    attributes:
+      label: requested RAM limit
+  - type: input
+    attributes:
+      label: requested timeout
+  - type: input
+    attributes:
+      label: requested number of targets
+  - type: textarea
+    attributes:
+      label: Why your crate needs the resource increases