CompatHelper: bump compat for Bijectors to 0.15, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the Bijectors package from 0.13, 0.14 to 0.13, 0.14, 0.15.
This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry.
It is your responsibility to make sure that your package tests pass before you merge this pull request.

[github-actions]

BridgeStan not found at location specified by $BRIDGESTAN environment variable, downloading version 2.5.0 to /home/runner/.bridgestan/bridgestan-2.5.0
Done!
Model dogs produces error: ErrorException("log_density() failed with exception: Exception: bernoulli_lpmf: Probability parameter is inf, but must be in the interval [0, 1] (in '/home/runner/work/JuliaBUGS.jl/JuliaBUGS.jl/benchmark/stan/bugs_examples/vol1/dogs/dogs.stan', line 37, column 6 to line 38, column 62)\n")

Model	Parameter Count	Data Count	Stan Density Time (µs)	Stan Density Gradient Time (µs)	JuliaBUGS Density Time with Graph Walk (µs)	JuliaBUGS Density Gradient Time with ReverseDiff.jl(compiled tape) (µs)
rats	65	150	5.8835	8.643	100.424	91.762
pumps	12	10	1.04456	1.37521	13.635	6.696
dogs	2	720	NA	NA	194.906	158.878
seeds	26	21	2.5698	3.20933	34.384	23.044
surgical_realistic	14	12	1.39071	1.79525	28.694	8.9565
magnesium	108	96	11.662	13.265	235.262	78.637
salm	22	18	2.5285	3.24056	23.594	13.305
equiv	15	20	2.7131	3.88014	35.627	16.341
dyes	9	30	1.09706	1.45275	19.536	13.936
stacks	6	21	1.28514	1.92592	41.367	16.32
epil	303	236	34.415	40.196	455.464	257.252
blockers	47	44	3.36263	3.96457	87.564	34.124
oxford	244	240	17.292	19.797	625.303	188.444
lsat	1006	5000	183.604	222.738	3080.67	1361.99
bones	33	422	71.434	92.263	627.787	195.687
mice	20	65	7.761	10.0753	49.632	40.275
kidney	64	58	11.1105	17.002	128.952	77.115
leuk	18	714	21.64	28.233	240.807	258.334
leukfr	40	714	24.707	33.132	281.228	322.876